Account Abstraction
A blockchain design where user accounts can have programmable validation logic, enabling features like social recovery and gas sponsorship.
Account-to-Account Payments (A2A)
Direct bank-to-bank transfers that bypass card networks, reducing costs for merchants and enabling instant settlement.
ACH Transfer
The Automated Clearing House network processes batch electronic payments in the US, handling payroll, bills, and bank transfers.
Acquirer (Acquiring Bank)
The bank or financial institution that processes card payments on behalf of a merchant, managing settlement and risk.
Acquiring Processor
A technology company that handles the technical transaction processing on behalf of acquiring banks, connecting merchants to card networks.
Adaptor Signature
A cryptographic primitive enabling conditional signatures that become valid only when a secret is revealed, powering trustless atomic protocols.
Address Gap Limit
The number of consecutive unused addresses a wallet scans before stopping, affecting fund discovery in HD wallets.
Address Reuse
Using the same Bitcoin address for multiple transactions, which degrades privacy by linking all activity to one identity.
Air-Gapped Signing
Signing Bitcoin transactions on a device permanently disconnected from any network, transferring data via QR codes or microSD cards.
Airdrop
Free distribution of tokens to wallet addresses, used for protocol launches, community rewards, and retroactive funding.
Algorithmic Stablecoin
A stablecoin that maintains its peg through automated supply adjustments rather than collateral reserves.
AMP (Atomic Multi-Path Payment)
A spontaneous multi-path payment protocol using base preimages that doesn't require an invoice from the recipient.
Anchor Outputs
Special outputs in Lightning commitment transactions that enable dynamic fee bumping during force closes, solving fee volatility issues in channel disputes.
Ark Protocol
A Bitcoin Layer 2 design using virtual UTXOs (vTXOs) and a coordinator to enable off-chain transfers with non-interactive recipient experience.
ASIC Miner
An Application-Specific Integrated Circuit designed exclusively for Bitcoin mining, vastly outperforming general-purpose hardware.
Asset-Referenced Tokens (ARTs)
A MiCA-defined category of crypto-assets that maintain stable value by referencing multiple currencies, commodities, or other assets, subject to strict EU reserve and governance requirements.
AssumeUTXO
A Bitcoin Core optimization that lets nodes start with a pre-validated UTXO set snapshot, becoming usable in minutes instead of hours.
AssumeValid
A Bitcoin Core optimization that skips signature verification for blocks below a hardcoded checkpoint, dramatically speeding up initial sync.
Atomic Multipath Payments (AMP)
A Lightning Network payment protocol that splits large payments across multiple paths using cryptographic secret sharing, ensuring all parts arrive or none do.
Atomic Swap
A trustless exchange of cryptocurrencies between two parties where either both transfers complete or neither does.
Authorization and Capture
The two-step card payment process: first reserving funds (authorization), then collecting them (capture) when the order is fulfilled.
Autoloop
An automated liquidity management system that uses rules-based submarine swaps to maintain optimal channel balances on Lightning Network nodes.
Automated Market Maker (AMM)
A smart contract that provides liquidity for token swaps using mathematical formulas instead of traditional order books.
BACS Payments
The UK's bulk payment system processing direct debits and credits with a 3-day clearing cycle for payroll and recurring payments.
Banking-as-a-Service (BaaS)
API-driven platforms that let non-bank companies embed banking features like accounts, cards, and payments into their products.
Batch Processing (Payments)
Grouping multiple payment transactions together for processing at scheduled intervals rather than individually in real-time.
Bech32 and Bech32m
Human-readable address encoding formats for SegWit and Taproot Bitcoin addresses, with error detection and no mixed-case confusion.
BGP Hijacking
An internet routing attack that can intercept Bitcoin network traffic by falsely advertising ownership of IP address ranges.
BIN (Bank Identification Number)
The first 6-8 digits of a payment card number that identify the issuing bank, card brand, and card type.
BIP-174 (PSBT Format)
The specification for Partially Signed Bitcoin Transactions, enabling offline signing and multi-party transaction construction.
BIP-32 (HD Wallets)
The Bitcoin Improvement Proposal defining hierarchical deterministic key derivation from a single master seed.
BIP-327 (MuSig2)
The specification for MuSig2, a two-round Schnorr multisignature protocol that produces a single aggregated signature indistinguishable from a regular single-signer signature on-chain.
BIP-340 (Schnorr Signatures for Bitcoin)
The specification defining how Schnorr signatures work in Bitcoin, using the secp256k1 curve with x-only public keys.
BIP-341 (Taproot Spending Rules)
The specification defining Taproot's output structure, key-path spending, and script-path spending via Merkle branches.
BIP-342 (Tapscript)
The specification defining the updated script validation rules for Taproot's script-path spending, with improved opcodes.
BIP-39 (Mnemonic Seed Phrases)
The standard defining how mnemonic word lists encode wallet seeds, enabling human-readable backup of Bitcoin keys.
BIP-44 (Multi-Account Hierarchy)
A standard derivation path structure for HD wallets, organizing keys by purpose, coin type, and account for interoperable wallet recovery.
BIP-47 (Reusable Payment Codes)
A protocol enabling reusable Bitcoin addresses through payment codes, improving privacy while maintaining a static identifier.
BIP-84 (Native SegWit Derivation)
The standard derivation path for native SegWit (bech32) addresses, using m/84'/0'/0' for the most fee-efficient Bitcoin address format.
BIP-86 (Taproot Derivation)
The standard derivation path for Taproot (P2TR) addresses, using m/86'/0'/0' for key-path-only spending.
Bitcoin Address Types
The different address formats used in Bitcoin, from legacy (1...) to SegWit (bc1q...) to Taproot (bc1p...), each with different features and fee costs.
Bitcoin Core
The reference implementation of the Bitcoin protocol, maintained by hundreds of contributors and running on the majority of full nodes.
Bitcoin Full Node
Software that validates every Bitcoin transaction and block against consensus rules, without trusting any third party.
Bitcoin Halving
The programmatic event every 210,000 blocks (~4 years) that cuts the mining reward in half, enforcing Bitcoin's fixed supply schedule.
Bitcoin Improvement Proposal (BIP)
The formal process for proposing and documenting changes to the Bitcoin protocol, similar to Python's PEPs or Ethereum's EIPs.
Bitcoin L2 Landscape
The ecosystem of Layer 2 protocols building on Bitcoin, from Lightning to sidechains to rollups, each with different trust and scaling tradeoffs.
Bitcoin Optech
A nonprofit providing technical resources, newsletters, and compatibility guides to help Bitcoin companies adopt scaling technologies.
Bitcoin Regtest
A local Bitcoin regression testing network where developers can instantly generate blocks on demand for automated testing.
Bitcoin Relay Network
Specialized networks that optimize block and transaction propagation between miners and nodes for faster distribution across the Bitcoin network.
Bitcoin RPC Interface
The JSON-RPC API that Bitcoin Core exposes for programmatic interaction, enabling wallet operations, node management, and blockchain queries.
Bitcoin Script
A stack-based programming language used to define spending conditions for Bitcoin outputs.
Bitcoin Script Limitations
The intentional constraints on Bitcoin's scripting language that prevent loops, limit stack size, and restrict computation for security.
Bitcoin Signet
A test Bitcoin network where blocks require a valid signature, providing a more predictable testing environment than testnet.
Bitcoin Testnet
A separate Bitcoin network using worthless coins for developers to test applications and protocol changes without risking real funds.
Bitcoin Transaction Lifecycle
The complete journey of a Bitcoin transaction from creation through signing, broadcast, mempool, confirmation, and finality.
BitVM
A computing paradigm enabling arbitrary computation verification on Bitcoin through optimistic fraud proofs, without consensus changes.
Blinded Paths
A privacy feature that hides the final destination of a payment by providing an encrypted route from an introduction point.
Block Confirmation
A block confirmation occurs each time a new block is added on top of the block containing a transaction, increasing settlement certainty.
Block Header
The 80-byte metadata structure at the start of each Bitcoin block containing the version, previous hash, Merkle root, timestamp, target, and nonce.
Block Propagation
The process of distributing newly mined blocks across the Bitcoin network, where speed is critical for mining fairness.
Block Size Limit
The maximum size of a Bitcoin block, currently measured in weight units (4M WU) after SegWit, constraining transaction throughput.
Block Subsidy
The newly minted Bitcoin awarded to miners for successfully mining a block, halving approximately every four years.
Block Template
The candidate block structure containing selected transactions that a miner attempts to find a valid hash for.
Block Time
The average interval between Bitcoin blocks, targeted at 10 minutes by the difficulty adjustment algorithm.
Blockchain Oracle
A service that feeds external data (prices, events, randomness) to smart contracts that can't access off-chain information directly.
Blockchain Pruning
Discarding historical block data after validation to save disk space while maintaining full consensus verification capabilities.
Blockchain Trilemma
The blockchain trilemma states that a blockchain can optimize for only two of three properties: decentralization, security, and scalability.
BOLT Specifications
The Basis of Lightning Technology documents that define the Lightning Network protocol standards.
BOLT-11 Invoice Format
The original Lightning payment request format encoding amount, destination, payment hash, and routing hints in a bech32 string.
BOLT-12 Offers
A new Lightning invoice format that enables reusable payment requests, subscriptions, and enhanced privacy through blinded paths.
BRC-20
An experimental fungible token standard on Bitcoin using Ordinals inscriptions to track token deployments, mints, and transfers.
Breez SDK
A development kit for building Lightning-enabled applications, abstracting channel management and liquidity complexity.
Bridge Security Models
The spectrum of trust assumptions in cross-chain bridges, from centralized custodians to trustless light client verification.
Bulletproofs
A zero-knowledge proof system for range proofs that requires no trusted setup, used for confidential transaction amounts.
Buy Now, Pay Later (BNPL)
A point-of-sale financing option that splits purchases into interest-free installments, offered by providers like Klarna and Affirm.
Card Network
Companies like Visa and Mastercard that set rules, route transactions, and provide infrastructure connecting card issuers and acquirers.
Card-Not-Present Payment (CNP)
An online or phone transaction where the physical card is absent, carrying higher fraud risk and interchange rates.
Card-Present Payment
An in-person transaction where the physical card or device is used at a terminal, offering lower fraud risk and interchange rates.
CBDC (Central Bank Digital Currency)
A digital form of a country's fiat currency issued directly by the central bank, aiming to modernize money and payments.
Censorship Resistance
Censorship resistance is a blockchain property ensuring no single entity can prevent valid transactions from being confirmed.
Chain Analysis (Blockchain Analytics)
The practice of analyzing blockchain transactions to identify, cluster, and trace activity for compliance, law enforcement, or intelligence.
Chain Reorganization (Reorg)
When a Bitcoin node switches to a longer valid chain, potentially reverting previously confirmed transactions.
Change Output
The UTXO returned to the sender when a Bitcoin transaction spends more than the payment amount, like getting change from cash.
Channel Capacity
The total amount of Bitcoin locked in a Lightning channel, representing the maximum that can be transferred in either direction.
Channel Factory
A proposed multi-party channel setup that enables efficient batch opening and closing of Lightning payment channels, significantly reducing on-chain footprint and improving scalability.
Channel Jamming
An attack that locks up Lightning channel liquidity by sending payments that are held indefinitely, degrading routing.
Channel Reserve
The minimum balance that must be maintained in a Lightning Network channel to ensure both parties can cover potential closure fees and prevent gaming the system.
Channel Reserve
A minimum balance each party must maintain in a Lightning channel, ensuring they have something to lose if they cheat.
Chantools
A command-line toolkit for Lightning Network channel recovery and troubleshooting, used to rescue funds from stuck, force-closed, or corrupted channels.
CHAPS Payments
The UK's real-time gross settlement system for high-value sterling payments, operated by the Bank of England.
Chargeback
A forced transaction reversal initiated by a cardholder's bank, designed to protect consumers but costing merchants billions annually.
Child-Pays-for-Parent (CPFP)
A fee-bumping technique where spending an unconfirmed output with a high-fee transaction incentivizes miners to include both.
CHIPS (Clearing House Interbank Payments System)
The Clearing House Interbank Payments System processes large-value US dollar payments between banks, settling $1.8 trillion daily.
Circuit Breaker (Lightning)
A Lightning node tool that rate-limits HTLC forwarding to protect against channel jamming and routing abuse.
Circular Rebalance
A Lightning Network liquidity management technique where node operators send payments to themselves through external routes to shift channel balances.
Clearing
The process of reconciling and netting payment obligations between banks before final settlement of funds.
Clipboard Hijacking
Malware that monitors the clipboard and replaces copied Bitcoin addresses with attacker-controlled addresses to redirect payments.
Closed-Loop Payment System
A payment network where the same entity controls issuance, processing, and settlement, like a gift card or proprietary wallet.
CLTV Expiry Delta
The number of blocks a Lightning routing node requires between incoming and outgoing HTLC timelocks to safely claim payments.
Cluster Mempool
Cluster mempool is a redesigned Bitcoin Core memory pool that groups related transactions for more optimal fee-based ordering.
Coin Control
Manually selecting which UTXOs to spend in a transaction, giving users control over privacy and fee optimization.
Coin Selection Algorithm
The algorithm a wallet uses to choose which UTXOs to spend, optimizing for fees, privacy, and UTXO set management.
Coinbase Field (Arbitrary Data)
The input data field in a coinbase transaction that miners can fill with arbitrary content, used for block height, pool identification, and messages.
Coinbase Maturity
The 100-block waiting period before newly mined Bitcoin can be spent, protecting against chain reorganization losses.
Coinbase Transaction
The first transaction in every Bitcoin block that creates new coins as the mining reward and collects transaction fees.
CoinJoin
A Bitcoin privacy technique where multiple users combine their transactions into one, making it difficult to trace which inputs paid which outputs.
Cold Storage
Storing cryptocurrency private keys on devices that are never connected to the internet, maximizing security against remote attacks.
Commitment Transaction
A pre-signed Bitcoin transaction representing the current balance of a Lightning channel, held by each party as insurance.
Commodity-Linked Synthetics
Digital assets that track the price of physical commodities like gold, silver, or oil through derivative mechanisms rather than direct physical backing.
Common-Input-Ownership Heuristic
The chain analysis assumption that all inputs in a Bitcoin transaction belong to the same entity, the most powerful tracing tool.
Compact Block Filters (Neutrino)
A privacy-preserving light client protocol where nodes download compact filters to find relevant blocks without revealing addresses.
Compact Blocks
A Bitcoin protocol optimization that reduces block propagation bandwidth by transmitting only short transaction IDs instead of full transactions.
Concentrated Liquidity Market Maker (CLMM)
An AMM design where liquidity providers can allocate capital within specific price ranges for higher capital efficiency.
Consensus Mechanism
A consensus mechanism is the protocol by which distributed nodes in a blockchain network agree on the current state of the ledger.
Contactless Payment (NFC)
A tap-to-pay transaction using NFC technology in cards or phones, enabling fast in-person payments without inserting cards.
Core Banking System
The central software platform that processes a bank's transactions, maintains accounts, and handles the ledger of record.
Core Lightning (CLN)
A modular Lightning implementation maintained by Blockstream, written in C with a plugin architecture for extensibility.
Correspondent Banking
A network of banking relationships enabling cross-border payments by routing funds through intermediary banks.
Covenant
A proposed Bitcoin feature that would allow outputs to restrict how they can be spent in future transactions.
Cross-Border Acquiring
Processing card payments for merchants in a different country than the acquirer, enabling global commerce with complex fee implications.
Cross-Border Payments
Financial transactions where the payer and recipient are in different countries, involving currency conversion and multiple intermediaries.
Cross-Chain Bridge
A protocol enabling asset or data transfer between different blockchains, with varying trust assumptions.
Cross-Chain Messaging
Protocols that transmit arbitrary data and instructions between blockchains, enabling cross-chain smart contract execution.
crvUSD Stablecoin
Curve Finance's stablecoin using a novel soft-liquidation mechanism called LLAMMA that gradually converts collateral instead of hard liquidations.
CTV (CheckTemplateVerify)
CheckTemplateVerify (BIP 119) is a proposed Bitcoin opcode enabling basic covenants by committing to a specific future transaction template.
DAI Stablecoin
A decentralized stablecoin generated by locking collateral in MakerDAO smart contracts, maintaining a soft dollar peg through overcollateralization and algorithmic stability mechanisms.
DAO (Decentralized Autonomous Organization)
An organization governed by smart contracts and token holder votes rather than traditional corporate hierarchy.
Data Availability
The guarantee that transaction data is published and accessible so anyone can verify state transitions and detect fraud.
Death Spiral
A self-reinforcing collapse mechanism in algorithmic stablecoins where falling prices trigger panic redemptions, further crashing the price until the peg breaks irreversibly.
Decentralized Exchange (DEX)
A non-custodial trading platform where users swap tokens directly from their wallets without depositing funds to a central party.
Decentralized Oracle Network
A network of independent nodes that aggregate off-chain data and deliver it to smart contracts with cryptographic guarantees.
DeFi Composability
The ability to combine multiple DeFi protocols into complex financial workflows, often called money legos.
DeFi Protocol Risk
The various risks of using DeFi protocols including smart contract bugs, oracle failures, governance attacks, and economic exploits.
DeFi Vault
A smart contract that automates a specific yield strategy, allowing users to deposit and earn without active management.
Depeg Event
When a stablecoin's market price diverges significantly from its target peg, often triggering panic and further instability.
Derivation Path
A hierarchical path specifying how to derive a specific key from a master seed in an HD wallet.
Difficulty Adjustment
Bitcoin's automatic mechanism to maintain approximately 10-minute block intervals by adjusting the mining difficulty every 2016 blocks.
Difficulty Epoch
The 2,016-block period between Bitcoin difficulty adjustments, approximately two weeks, during which the difficulty target remains constant.
Direct Debit
A recurring pull payment arrangement where a business is authorized to collect payments directly from a customer's bank account.
Disbursement
The outward payment of funds from a business to individuals, including payroll, refunds, insurance payouts, and vendor payments.
Discreet Log Contract (DLC)
A Bitcoin smart contract that uses oracle signatures to settle bets and financial derivatives without revealing contract details on-chain.
Dispute Resolution (Payments)
The formal process for handling transaction disagreements between cardholders, merchants, and banks under card network rules.
Dollar-Denominated Savings
Using dollar-pegged stablecoins as a savings vehicle in countries with high inflation or limited banking access.
Double Spend
An attack where the same Bitcoin is spent in two conflicting transactions, attempting to defraud a recipient.
Dual-Funded Channel
A Lightning channel where both parties contribute funds to the opening transaction, providing immediate bidirectional capacity.
Dust Attack
Sending tiny amounts of Bitcoin to many addresses to track spending patterns and deanonymize users when dust is consolidated.
Dust Limit
The minimum UTXO value that Bitcoin Core will create or relay, below which the output costs more in fees to spend than it's worth.
E-Money License (EMI)
A European license authorizing companies to issue electronic money and provide payment services across the EU.
E-Money Tokens (EMTs)
A type of stablecoin under MiCA regulation that is pegged to a single fiat currency and backed by reserves, functioning as a digital representation of electronic money.
eCash (Chaumian eCash)
A digital cash system using blind signatures to enable private, untraceable payments through a mint, pioneered by David Chaum.
Eclair
A Scala-based Lightning implementation by ACINQ, powering the Phoenix mobile wallet and enterprise Lightning deployments.
Eclipse Attack
An attack isolating a node by controlling all its peer connections, enabling double spends or selfish mining against that node.
Electrum Server
A backend service that indexes the Bitcoin blockchain to efficiently serve wallet queries, enabling lightweight clients without full node resources.
Eltoo
A proposed Lightning Network channel update mechanism using SIGHASH_ANYPREVOUT that simplifies state management by allowing any later state to replace any earlier state.
Embedded Finance
Integrating financial services like payments, lending, or insurance directly into non-financial apps and platforms.
EMV Chip
The global smart card standard using embedded microchips for secure card-present transactions, replacing vulnerable magnetic stripes.
Ephemeral Dust
Temporary dust outputs in Lightning commitment transactions that allow channels to use their full balance without reserving funds for on-chain fees.
Erlay
A proposed Bitcoin protocol improvement that reduces transaction relay bandwidth by 40% using set reconciliation instead of flooding.
EURC (Euro Coin)
A euro-backed stablecoin issued by Circle, providing a regulated digital euro for cross-border payments and DeFi.
Extended Key (xprv/xpub)
A key plus chain code that enables deriving child keys in an HD wallet, with extended private keys (xprv) or public keys (xpub).
Faster Payments
The UK's real-time payment system processing domestic bank transfers in seconds, available 24/7 since 2008.
FBO Account (For Benefit Of)
A bank account held by a fintech or platform on behalf of its end users, where funds belong to the users, not the company.
Fedimint
A federated custody and payment protocol for Bitcoin communities, using threshold cryptography to create community-run Bitcoin banks.
FedNow
The Federal Reserve's instant payment service enabling 24/7/365 real-time settlement between US banks and credit unions.
Fedwire
The Federal Reserve's real-time gross settlement system for high-value, time-critical US dollar payments between banks.
Fee Estimation
Algorithms that predict the optimal transaction fee rate for timely Bitcoin block inclusion based on mempool conditions.
Fee Sniping
A theoretical mining attack where miners re-mine recent blocks to capture high-fee transactions, threatening finality.
Fiat-Backed Stablecoin
A stablecoin maintaining its peg through reserves of fiat currency or fiat-equivalent assets held by a centralized custodian.
Finality
The point at which a transaction becomes irreversible and cannot be undone, varying by system design.
Flash Loan
An uncollateralized DeFi loan that must be borrowed and repaid within the same blockchain transaction, enabling atomic arbitrage.
Float (Payments)
Money in transit between sender and receiver that hasn't yet settled, representing both a risk and a revenue opportunity.
Force Close
Unilaterally closing a Lightning channel by broadcasting the latest commitment transaction when the counterparty is unresponsive or malicious.
Fraud Proof
A mechanism where anyone can challenge an invalid state transition by proving the computation was incorrect, used in optimistic rollups.
FRAX Stablecoin
A stablecoin that evolved from fractional-algorithmic design to fully collateralized, pioneering the hybrid stability approach.
Friendly Fraud
When a legitimate cardholder disputes a valid transaction, either intentionally (chargeback fraud) or due to confusion about the charge.
Front-Running
Exploiting advance knowledge of pending transactions to place profitable trades before them, common in DeFi and DEXs.
FROST (Flexible Round-Optimized Schnorr Threshold)
A threshold Schnorr signature scheme enabling t-of-n signing with just two communication rounds, optimal for distributed custody.
Full RBF (Full Replace-by-Fee)
Full RBF is a mempool policy where any unconfirmed transaction can be replaced by a higher-fee version, regardless of opt-in signaling.
Funding Rate
The periodic payment between long and short traders in perpetual futures markets that keeps the contract price anchored to the spot price.
Fungibility
Fungibility is the property where each unit of a currency is interchangeable and indistinguishable from any other unit of equal value.
FX Spread
The difference between the buy and sell price of a currency pair, representing a hidden cost in cross-border payments.
Genesis Block
The first block in the Bitcoin blockchain, mined by Satoshi Nakamoto on January 3, 2009, containing a famous newspaper headline.
GENIUS Act
Proposed US legislation establishing a federal framework for payment stablecoin issuance, reserves, and supervision.
GHO Stablecoin
Aave's decentralized stablecoin minted by borrowers using their Aave collateral, with interest rates set by governance.
Gossip Protocol (Lightning)
The peer-to-peer protocol Lightning nodes use to share information about channels, nodes, and fee policies across the network.
Governance Token
A crypto token granting holders voting rights over a protocol's parameters, upgrades, and treasury spending decisions.
Great Consensus Cleanup
The Great Consensus Cleanup is a proposed Bitcoin soft fork that fixes several long-standing consensus bugs and edge cases.
Greenlight
Blockstream's cloud-hosted Lightning node service where users keep their keys but the node runs in the cloud for reliability.
Hard Fork
A non-backward-compatible protocol change that creates a permanent chain split if not all nodes upgrade, dividing the network.
Hardened Derivation
An HD wallet key derivation method that prevents child public keys from being derived from the parent public key alone, protecting against key compromise cascades.
Hashrate
The total computational power dedicated to Bitcoin mining, measured in hashes per second, indicating network security strength.
Hawala
An informal value transfer system based on trust networks, where money is sent without physical movement through local agents.
HD Wallet (Hierarchical Deterministic Wallet)
A wallet that derives all keys from a single master seed, enabling backup with just a seed phrase and organized key hierarchies.
Hodl Invoice
A Lightning invoice where the receiver can delay settlement, enabling escrow-like functionality and conditional payments on the Lightning Network.
Hot Wallet
A cryptocurrency wallet connected to the internet for convenient access and transactions, accepting higher security risk.
HSM (Hardware Security Module)
Enterprise-grade hardware devices for generating, storing, and using cryptographic keys with FIPS 140-2/3 certification.
HTLC (Hash Time-Locked Contract)
A conditional payment mechanism using hash locks and time locks for trustless atomic transactions across payment channels.
Hybrid Collateral Ratio
A stablecoin design mechanism that dynamically adjusts the mix of asset-backed collateral and algorithmic stabilization to maintain price peg.
IBAN (International Bank Account Number)
The International Bank Account Number is a standardized format for identifying bank accounts across borders in 80+ countries.
Impermanent Loss
The opportunity cost LPs face when the price ratio of pooled tokens changes, resulting in less value than simply holding the tokens.
Inbound Liquidity
The capacity to receive Lightning payments, determined by how much of a channel's balance sits on the remote side.
Initial Block Download (IBD)
The process of downloading and validating the entire Bitcoin blockchain when setting up a new full node, taking hours to days.
Instant Settlement
Settlement of payment transactions in real-time or near-real-time, eliminating the traditional multi-day delay between payment and fund availability.
Intent-Based Trading
A trading paradigm where users express desired outcomes and solvers compete to find the optimal execution path across venues.
Interac e-Transfer
Canada's real-time person-to-person payment system enabling instant bank transfers using email or phone number.
Interchange Fee
The fee paid by the merchant's bank to the cardholder's bank on each card transaction, set by card networks like Visa and Mastercard.
Interchange-Plus Pricing
A transparent payment processing pricing model where the merchant pays actual interchange plus a fixed markup from the processor.
ISO 20022
A global messaging standard for financial transactions enabling richer, structured payment data across banks and payment systems.
Issuer (Issuing Bank)
The bank that issues credit or debit cards to consumers, approving or declining transactions and bearing fraud risk.
JIT Channel (Just-in-Time)
A Lightning channel opened on-the-fly when a payment arrives, allowing users to receive their first payment without pre-existing channels.
Justice Transaction
A penalty transaction that sweeps all funds from a cheating counterparty's Lightning channel, enforcing protocol rules and deterring fraud attempts.
Key Ceremony
A formal, audited process for generating, distributing, or using high-value cryptographic keys with witnesses and security controls.
Key Management
The practices and systems for generating, storing, using, and backing up cryptographic keys that control digital assets.
Key Rotation
Periodically generating new cryptographic keys and migrating funds from old keys, limiting exposure from potential key compromise.
Keysend
A Lightning Network payment method that enables spontaneous payments without requiring an invoice from the recipient.
KYC/AML
Know Your Customer and Anti-Money Laundering regulations requiring financial institutions to verify identities and monitor for illicit activity.
Layer 2
A protocol built on top of a base blockchain that processes transactions off-chain while inheriting the security of the underlying layer.
LDK (Lightning Dev Kit)
A flexible Lightning library that lets developers embed Lightning functionality directly into applications without running a standalone node.
Ledger (Accounting)
A systematic record of financial transactions organized into accounts, forming the foundation of all financial record-keeping.
Lending Protocol
A DeFi platform enabling permissionless borrowing and lending of crypto assets with algorithmic interest rates set by supply and demand.
Lightning Address
An email-like identifier (user@domain.com) that resolves to a Lightning invoice, making payments as easy as sending an email.
Lightning Channel
A two-party payment channel funded by an on-chain Bitcoin transaction that enables unlimited off-chain transactions between participants.
Lightning Invoice
A payment request containing the amount, destination, payment hash, and routing hints needed to send a Lightning payment.
Lightning Network vs Spark
A comparison of the two Bitcoin Layer 2 approaches: Lightning's payment channels vs Spark's statechain-based architecture.
Lightning Service Provider (LSP)
A service that manages Lightning channels and liquidity on behalf of users, enabling seamless mobile wallet experiences.
Limit Order (DeFi)
A DeFi order to swap tokens at a specified price or better, executed when market conditions meet the trader's terms.
Liquid Network
A federated Bitcoin sidechain by Blockstream offering confidential transactions, faster settlement, and issued assets for traders and institutions.
Liquid Restaking
A protocol that takes already-staked assets and restakes them to secure additional protocols, earning multiple layers of yield while maintaining token liquidity.
Liquid Staking
A DeFi mechanism that issues tradeable tokens representing staked assets, unlocking liquidity while maintaining staking rewards.
Liquidation (DeFi)
The forced sale of a borrower's collateral when its value drops below the required ratio, protecting lenders from bad debt.
Liquidation Cascade
A chain reaction of forced collateral liquidations triggered when market crashes push multiple DeFi vaults below their minimum collateralization thresholds simultaneously.
Liquidity Ads
A protocol for Lightning nodes to advertise and sell channel liquidity in a decentralized marketplace.
Liquidity Bootstrapping Pool (LBP)
A token launch mechanism using weighted AMM pools that shift over time, enabling fair price discovery without front-running.
Liquidity Fragmentation
The spreading of trading liquidity across multiple chains, DEXs, and pools, making it harder to execute large trades efficiently.
Liquidity Provider (LP)
A user who deposits tokens into a DeFi protocol's liquidity pool, earning fees from trades executed against their capital.
LND (Lightning Network Daemon)
The most widely deployed Lightning implementation, built by Lightning Labs in Go, powering the majority of Lightning nodes.
LNURL
A set of HTTP-based protocols extending Lightning with features like auth, pay, withdraw, and channel requests via simple URLs.
Locktime (nLockTime)
A transaction-level field that prevents a Bitcoin transaction from being included in a block until a specified time or block height.
Loop In/Out
Submarine swap mechanisms for moving funds between on-chain Bitcoin and Lightning Network without custody, enabling non-custodial liquidity management.
LUSD (Liquity USD)
An immutable, governance-free stablecoin backed only by ETH collateral, generated through the Liquity protocol.
Mainnet
A mainnet is the primary live blockchain network where real transactions with economic value are broadcast and recorded.
Market Maker
A participant that continuously quotes buy and sell prices for an asset, providing liquidity and earning the bid-ask spread.
MAST (Merkelized Alternative Script Trees)
A Taproot feature enabling multiple spending conditions organized in a Merkle tree, revealing only the used condition on-chain.
Mempool
Each Bitcoin node's waiting area for unconfirmed transactions, where transactions compete for block inclusion based on fee rates.
Merchant Discount Rate (MDR)
The total percentage fee a merchant pays per card transaction, comprising interchange, scheme fees, and acquirer markup.
Merchant of Record (MoR)
The entity that appears on a customer's bank statement and bears responsibility for the transaction, taxes, and disputes.
Merkle Tree
A binary tree of hashes used in Bitcoin blocks to efficiently prove transaction inclusion with minimal data.
MEV (Maximal Extractable Value)
The profit available by reordering, inserting, or censoring transactions within a block, extracted by validators and searchers.
MEV Supply Chain
The ecosystem of searchers, builders, and validators that discover, extract, and distribute value from transaction ordering on blockchains like Ethereum.
MiCA (Markets in Crypto-Assets)
The EU's comprehensive crypto regulation framework covering stablecoins, exchanges, and service providers, effective from 2024.
Mining Pool
A group of miners combining hashrate to find blocks more frequently and share rewards proportionally, reducing income variance.
Mining Reward
The total compensation miners receive per block: the block subsidy (newly created BTC) plus all transaction fees included in the block.
Miniscript
A structured subset of Bitcoin Script that enables analysis, composition, and generic signing of spending conditions.
Mint/Burn Mechanism
The process of creating new stablecoin tokens when assets are deposited and destroying them upon redemption.
Mobile Money
A phone-based financial service enabling unbanked users to store, send, and receive money without a traditional bank account.
Modular Blockchain
A blockchain architecture separating execution, consensus, data availability, and settlement into specialized layers for scalability.
Money Services Business (MSB)
A FinCEN classification for businesses involved in money transmission, currency exchange, check cashing, or stored value.
Money Transfer Operator (MTO)
A non-bank company specializing in cross-border remittances, like Western Union and Wise, often serving unbanked populations.
Money Transmitter License
A state-level US license required to transmit money or provide payment services, with each state having its own requirements.
MPC Wallet
A wallet using multi-party computation to distribute key material across multiple parties, eliminating single points of failure.
MPP (Multipath Payments)
A Lightning payment split across multiple routes that recombines atomically at the destination for improved reliability.
Multi-Path Payments (MPP)
A Lightning feature that splits a single payment across multiple routes to improve success rates and enable larger payments.
Multisig Wallet
A Bitcoin wallet requiring multiple private keys to authorize transactions, providing shared control and eliminating single points of failure.
Network Token
A card network-issued token replacing the actual card number, improving authorization rates and reducing fraud across merchants.
NFT (Non-Fungible Token)
A unique digital asset with verifiable ownership on blockchain, representing art, collectibles, gaming items, or real-world assets.
Nonce
A number used once in Bitcoin mining that miners iterate through to find a block hash below the difficulty target.
Nostro and Vostro Accounts
Mirror accounts held between correspondent banks: a nostro (our account at your bank) and vostro (your account at our bank).
Omnibus Wallet
A single blockchain wallet holding funds for multiple users, with individual balances tracked in an off-chain database.
On-Chain vs Off-Chain
On-chain transactions are recorded directly on the blockchain, while off-chain transactions occur on secondary layers and settle later.
On-Ramp / Off-Ramp
Services converting between fiat currency and cryptocurrency, enabling users to enter and exit the crypto economy.
Onion Routing
A layered encryption technique where each routing node can only decrypt its own instructions, preserving sender and receiver privacy.
OP_CAT (Proposed)
A proposed Bitcoin opcode to concatenate two stack elements, potentially enabling covenants and advanced smart contracts on Bitcoin.
OP_CHECKLOCKTIMEVERIFY (OP_CLTV)
A Bitcoin Script opcode that prevents an output from being spent until a specified block height or timestamp.
OP_CHECKMULTISIG
A legacy Bitcoin Script opcode for m-of-n multisignature verification, replaced by OP_CHECKSIGADD in Tapscript.
OP_CHECKSEQUENCEVERIFY (OP_CSV)
A Bitcoin Script opcode that enforces a relative timelock, requiring a minimum number of blocks since the input was confirmed.
OP_CHECKSIG
The Bitcoin Script opcode that verifies a digital signature against a public key, the most fundamental operation in Bitcoin transactions.
OP_IF / OP_NOTIF
Bitcoin Script flow control opcodes that enable conditional execution paths, essential for complex contracts like HTLCs.
OP_RETURN
A Bitcoin script opcode that marks an output as provably unspendable, commonly used to embed arbitrary data in transactions.
OP_VAULT (Proposed)
A proposed Bitcoin opcode specifically designed to enable vault contracts with secure recovery and withdrawal delay mechanisms.
Open Banking
Regulatory frameworks requiring banks to share customer financial data with authorized third parties via secure APIs.
Open-Loop Payment System
A payment network where cards or credentials are accepted across multiple merchants and institutions, like Visa or Mastercard.
Optimistic Rollup
A Layer 2 scaling solution that assumes transactions are valid by default and uses fraud proofs to handle disputes.
Oracle Manipulation
An attack vector where malicious actors distort price feeds used by smart contracts, often to trigger unjust liquidations or exploit arbitrage in collateralized protocols.
Order Book DEX
A decentralized exchange matching buy and sell orders at specific prices, offering familiar trading mechanics without centralized custody.
Ordinals
A protocol for inscribing arbitrary data to individual satoshis, creating Bitcoin-native digital artifacts and NFTs.
Orphan Block (Stale Block)
A valid block that is not part of the longest chain because another block at the same height was accepted first by the network.
Output Descriptor
A standardized format describing how Bitcoin addresses are derived, enabling precise wallet backup and restoration across different software.
Overcollateralization
Requiring collateral worth more than the borrowed or minted amount to provide a safety buffer against price volatility.
P2PKH (Pay-to-Public-Key-Hash)
The original Bitcoin address format starting with '1', paying to the hash of a public key for basic single-signature transactions.
P2SH (Pay-to-Script-Hash)
A Bitcoin address format starting with '3' that pays to the hash of a script, enabling multisig and complex spending conditions.
P2TR (Pay-to-Taproot)
The Taproot address format starting with 'bc1p', supporting both key-path and script-path spending with enhanced privacy.
P2WPKH (Pay-to-Witness-Public-Key-Hash)
The native SegWit address format for single-signature transactions, starting with 'bc1q' and offering the lowest fees before Taproot.
P2WSH (Pay-to-Witness-Script-Hash)
The native SegWit address format for script-based transactions like multisig, offering larger script capacity than P2SH.
Package Relay
Package relay is a Bitcoin protocol upgrade allowing nodes to evaluate groups of related transactions together for mempool acceptance.
Passkeys (WebAuthn/FIDO2)
A passwordless authentication standard using public key cryptography, increasingly adopted for crypto wallet access.
Passphrase (25th Word)
An optional password added to a seed phrase that derives an entirely different set of keys, enabling plausible deniability.
PayJoin
A privacy-enhancing Bitcoin payment where both sender and receiver contribute inputs, breaking chain analysis assumptions.
Payment Aggregator
A company that bundles many small merchants under a single merchant account, simplifying onboarding but sharing risk exposure.
Payment Channel Network
A mesh of interconnected payment channels enabling multi-hop transactions, with Lightning Network being the largest example.
Payment Facilitator (PayFac)
A company that processes payments on behalf of sub-merchants under its own merchant account, simplifying onboarding.
Payment Finality
The point at which a payment becomes irrevocable and cannot be recalled, varying dramatically across different payment systems.
Payment Fraud
Criminal exploitation of payment systems through identity theft, account takeover, counterfeit cards, or social engineering.
Payment Gateway
Software that securely transmits payment data from a merchant's checkout to the payment processor for authorization.
Payment Hash
A SHA-256 hash of the preimage that serves as the conditional lock for an HTLC payment in Lightning.
Payment Initiation Service (PIS)
A regulated service under PSD2 that initiates bank payments on behalf of users, enabling checkout without card networks.
Payment Orchestration
Software that routes transactions across multiple payment providers to optimize authorization rates, costs, and redundancy.
Payment Orchestration Platform
A middleware layer that connects to multiple PSPs, acquirers, and payment methods to optimize routing, reduce costs, and increase resilience.
Payment Probe
A technique to discover channel balances and route viability by sending payments designed to fail at the destination.
Payment Processor
A company that handles the technical routing of card transactions between merchants, card networks, and issuing banks.
Payment Rails
The underlying infrastructure and networks that move money between parties, from legacy card networks to modern blockchain systems.
Payment Service Provider (PSP)
A company offering merchants the technology and banking relationships to accept electronic payments across multiple methods.
Payment Settlement Cycle
The time between a payment transaction and when the merchant receives the funds, typically T+1 to T+3 for card payments.
Payment Surcharging
Adding an extra fee at checkout when customers pay by card, passing processing costs to the cardholder rather than absorbing them.
PCI DSS
The Payment Card Industry Data Security Standard, a set of requirements for organizations that handle credit card data.
Pedersen Commitment
A cryptographic commitment scheme that hides a value while allowing mathematical operations, used in confidential transactions.
Peg Mechanism
The system of incentives, arbitrage, and backing that maintains a stablecoin's price at its target value.
Penalty Transaction
A transaction that claims all funds in a Lightning channel when a counterparty broadcasts an outdated commitment transaction, enforcing honest behavior through severe financial consequences.
Perpetual Futures
Crypto derivative contracts with no expiry date that track an underlying asset's price through funding rate payments between longs and shorts.
Phishing Attack
A social engineering attack using fake websites, emails, or messages to trick users into revealing private keys, seed phrases, or passwords.
PIX Payments
Brazil's instant payment system launched by the central bank, enabling free 24/7 transfers and becoming the country's dominant payment method.
Plasma
An early Ethereum Layer 2 design using exit games for security, largely superseded by rollups but influential in L2 research.
Precision Decay
Cumulative rounding errors in fixed-point arithmetic during multi-hop swaps that can be exploited to drain liquidity pools; a vulnerability class flagged in numerous DeFi security audits.
Preimage
The secret value that, when hashed, produces the payment hash and unlocks an HTLC to claim a Lightning payment.
Private Channel (Unannounced)
A Lightning channel not broadcast to the network gossip protocol, known only to the two participants and used via route hints.
Private Key
A secret 256-bit number that controls Bitcoin ownership, used to sign transactions proving authorization to spend funds.
Probing
A technique used to discover Lightning Network channel balances and network topology by sending fake payments that reveal routing information.
Programmable Money
Digital currency with embedded rules governing how, when, and by whom it can be spent, enabling automated financial logic.
Proof of Stake (PoS)
Proof of stake is a consensus mechanism where validators lock up cryptocurrency as collateral to propose and attest to new blocks.
Proof of Work (PoW)
Proof of work is a consensus mechanism where miners expend computational energy to validate transactions and secure the blockchain.
Proposer-Builder Separation (PBS)
A blockchain design separating block construction (builders) from block proposal (validators) to manage MEV distribution.
Pruned Node
A Bitcoin full node that discards old block data after validation, significantly reducing storage requirements while maintaining full validation.
PSBT (Partially Signed Bitcoin Transaction)
A standardized format for constructing and signing Bitcoin transactions across multiple parties or devices.
PTLC (Point Time-Locked Contract)
An improved conditional payment mechanism using Schnorr signatures and adaptor signatures instead of hash locks.
Public Key
A point on the secp256k1 elliptic curve derived from a private key, used to verify signatures and generate Bitcoin addresses.
Pull Payment
A payment where the recipient initiates the charge against the payer's account, common in subscriptions and recurring billing.
Push Payment
A payment initiated and authorized by the sender, giving them full control over when and how much to send.
PYUSD (PayPal USD)
PayPal's dollar-backed stablecoin issued by Paxos, available to PayPal and Venmo users for payments and transfers.
Real-Time Payments
Payment systems that transfer and settle funds within seconds, available 24/7, replacing batch-processed legacy rails.
Real-World Assets (RWA)
Traditional financial assets like Treasury bills, bonds, and real estate tokenized on blockchain for DeFi composability.
Rebasing Token
A token that automatically adjusts wallet balances to reflect yield or maintain a peg, changing supply rather than price.
Reconciliation
The process of matching internal records with external payment data to ensure all transactions are accurately accounted for.
Recurring Billing
Automatically charging a customer at regular intervals for subscriptions and memberships, requiring stored payment credentials.
Remittance Corridor
A specific geographic route for cross-border money transfers, with costs and speeds varying dramatically by corridor.
Replace-By-Fee (RBF)
A Bitcoin mempool policy allowing unconfirmed transactions to be replaced with higher-fee versions.
Replay Attack
Reusing a valid transaction or signature on a different chain or context where it wasn't intended.
Request to Pay
A payment messaging standard that lets billers send payment requests directly to a payer's bank app for approval.
Reserve Proof
Cryptographic or audit-based evidence that a stablecoin issuer holds sufficient assets to back all outstanding tokens.
Revocation Key
A cryptographic key derived during Lightning Network channel updates that allows a counterparty to claim all channel funds if an old, revoked commitment transaction is broadcast.
RGB Protocol
A Bitcoin Layer 2 for smart contracts and token issuance using client-side validation, keeping contract data off-chain.
RIPEMD-160
A 160-bit hash function used in Bitcoin address generation to shorten public key hashes, combined with SHA-256 in HASH160.
Risk Scoring
Assigning a numerical fraud probability to each transaction using machine learning models analyzing hundreds of data signals.
Rollup
A Layer 2 scaling solution that executes transactions off-chain and posts compressed data or proofs to the base layer for security.
Route Hints
Routing information embedded in Lightning invoices that enable payments to nodes with private or unannounced channels.
Routing Attack
Attacks targeting Lightning Network payment routing, including fee manipulation, channel jamming, and balance probing.
Routing Fees
The fees charged by Lightning nodes to forward payments through their channels, consisting of a base fee and a proportional fee.
RSK (Rootstock)
A Bitcoin sidechain with Ethereum-compatible smart contracts, secured by merge-mining with Bitcoin miners.
RTP Network
The Clearing House's Real-Time Payments network, the first US real-time payment system, enabling instant bank-to-bank transfers.
Runes
A UTXO-based fungible token protocol on Bitcoin designed to be more efficient than BRC-20 by using OP_RETURN instead of inscriptions.
Sandwich Attack
An MEV strategy where an attacker front-runs and back-runs a victim's DEX trade, profiting from the price impact they cause.
Scheme Fee
The fee charged by card networks (Visa, Mastercard) for using their infrastructure, branding, and dispute resolution systems.
Schnorr Signatures
A digital signature scheme enabled by Taproot that offers smaller signatures, native multisig aggregation, and improved privacy.
ScriptPubKey (Output Script)
The locking script placed on a Bitcoin transaction output that defines the conditions required to spend those funds.
ScriptSig (Input Script)
The unlocking script provided when spending a Bitcoin output, containing signatures and data that satisfy the output's spending conditions.
secp256k1
The specific elliptic curve used by Bitcoin for all public key cryptography, chosen by Satoshi for its efficiency and security properties.
Secure Element
A tamper-resistant chip that stores cryptographic keys and performs signing operations in hardware wallets and mobile devices, protecting against physical and software attacks.
Seed Phrase
A human-readable list of words (typically 12 or 24) that encodes the master seed for an HD wallet.
SegWit (Segregated Witness)
A Bitcoin protocol upgrade that separates signature data from transaction data, fixing malleability and increasing effective block capacity.
Self-Custody
Holding your own private keys rather than trusting a third party, embracing the principle of not your keys, not your coins.
Selfish Mining
A mining strategy where a miner withholds discovered blocks to gain a disproportionate share of rewards, at the network's expense.
SEPA Transfer
The Single Euro Payments Area enables euro-denominated bank transfers across 36 European countries with standardized rules.
Sequence Number
A per-input field in Bitcoin transactions used for relative timelocks (BIP-68) and signaling Replace-By-Fee (BIP-125).
Settlement
The final, irrevocable transfer of value that completes a transaction, often requiring on-chain confirmation.
SHA-256
The cryptographic hash function at the core of Bitcoin mining, address generation, and transaction integrity verification.
Shamir's Secret Sharing
A cryptographic scheme that splits a secret into multiple shares, where any k-of-n shares can reconstruct the original secret.
Shor's Algorithm Vulnerability
A quantum computing threat to elliptic curve cryptography (ECC) that could theoretically break the digital signatures securing Bitcoin and stablecoin transactions.
Sidechain
A separate blockchain pegged to a parent chain, enabling different features or tradeoffs while maintaining asset transferability.
Sighash Flag
A flag in Bitcoin signatures specifying which parts of the transaction the signature commits to, enabling flexible signing schemes.
Signing Device
A dedicated hardware device that stores private keys and signs transactions, isolating keys from general-purpose computers.
Silent Payments
A proposed Bitcoin protocol for generating unique addresses from a static public identifier, enabling private donations without interaction.
SIM Swap Attack
A social engineering attack where an attacker convinces a carrier to transfer a victim's phone number, intercepting 2FA codes.
Slippage
The difference between the expected price and executed price of a trade, caused by low liquidity or large order size.
Social Recovery Wallet
A wallet design where trusted guardians can help recover access if the owner loses their key, without guardians having spending power.
Soft Fork
A backward-compatible Bitcoin protocol upgrade where old nodes still accept new blocks, enabling gradual adoption of new rules.
Sovereign Rollup
A rollup that uses the base layer only for data availability, with its own nodes verifying execution independently.
Specified Stablecoins
A regulatory classification in Hong Kong for fiat-referenced stablecoins with official currency ties, subject to mandatory licensing requirements.
SPEI (Sistema de Pagos Electrónicos Interbancarios)
Mexico's electronic interbank payment system providing near-instant peso transfers between bank accounts 24/7.
Splicing
A technique to add or remove funds from a Lightning channel without closing it, maintaining channel uptime and routing capabilities.
Sponsor Bank
A chartered bank that provides regulatory and banking infrastructure for fintech companies to offer financial services.
SPV Client (Simplified Payment Verification)
A lightweight Bitcoin client that verifies transactions using block headers and Merkle proofs without downloading the full blockchain.
Stablecoin Arbitrage
Trading strategies that profit from price deviations between a stablecoin's market price and its peg, helping maintain stability.
Stablecoin Blacklist (Freeze Function)
The ability of centralized stablecoin issuers to freeze or blacklist specific addresses, preventing them from transacting.
Stablecoin Payment Rails
Using stablecoins as the settlement layer for payments, enabling instant cross-border transfers at near-zero cost.
Stablecoin Reserves
The assets backing a stablecoin's value, ranging from cash and Treasuries to crypto collateral and real-world assets.
Stablecoin Risk Assessment
A framework for evaluating stablecoin safety based on reserves, governance, legal structure, and redemption mechanics.
Stablecoin Savings Rate
Interest earned by depositing stablecoins into protocol-native savings contracts, like MakerDAO's DSR or sDAI.
Stablecoin Supply and Market Cap
The total outstanding value of stablecoins in circulation, a key indicator of crypto market liquidity and adoption.
Stablecoin Trilemma
The design tradeoff between decentralization, capital efficiency, and price stability that every stablecoin must navigate.
Stablecoin Yield
Returns earned on stablecoin deposits through lending, liquidity provision, or issuer revenue sharing programs.
Staking
Locking up cryptocurrency as collateral to participate in proof-of-stake consensus, earning rewards for securing the network.
State Channel
A Layer 2 construct where participants exchange signed state updates off-chain, with on-chain settlement only for disputes.
Statechains
A Layer 2 protocol enabling off-chain transfer of UTXO ownership through co-signing key rotation with a statechain entity.
Static Channel Backup (SCB)
A backup file containing the information needed to recover Lightning channel funds by triggering force-closes with channel partners.
Stored Value
Prepaid funds loaded onto a card, account, or digital wallet that can be spent until depleted, like gift cards or transit cards.
Strategic Bitcoin Reserve
Learn what a strategic bitcoin reserve is: a government or institutional stockpile of bitcoin held as a long-term reserve asset.
Stratum Protocol
The communication protocol between Bitcoin miners and mining pools, with Stratum V2 adding encryption and decentralized block templates.
Strong Customer Authentication (SCA)
A European regulation requiring two-factor verification for electronic payments, reshaping online checkout experiences across the EU.
Submarine Swap
An atomic exchange between on-chain Bitcoin and Lightning payments, enabling trustless movement of funds between layers.
Supply Chain Attack (Hardware Wallets)
Tampering with hardware wallets during manufacturing or shipping to extract private keys or install malicious firmware.
SWIFT Network
The global messaging network connecting 11,000+ banks to coordinate cross-border payments and financial communications.
Sybil Attack
An attack where a single adversary creates many fake identities to gain disproportionate influence over a network.
Synthetic Asset
A token that tracks the price of an external asset through oracles and collateralization rather than direct backing.
Taint Analysis
Tracking the flow of Bitcoin from known-bad addresses through subsequent transactions to identify contaminated funds.
Taproot
A Bitcoin upgrade activating Schnorr signatures, MAST, and Tapscript for improved privacy, efficiency, and smart contract capabilities.
Taproot Assets (TAP)
Learn what Taproot Assets is: a Bitcoin protocol for issuing stablecoins, tokens, and NFTs on-chain using Taproot transactions.
Tapscript
Tapscript is the upgraded scripting language used inside Taproot script-path spends, enabling new opcodes and improved flexibility.
Threshold Signature
A cryptographic scheme where t-of-n parties must cooperate to produce a valid signature, without any party holding the complete key.
Time-Bandit Attack
A theoretical attack where miners with sufficient hashrate reorg past blocks to steal high-value transactions or manipulate history.
Timelock
A Bitcoin script condition that prevents spending until a specified block height or timestamp is reached.
Token Bridge
Infrastructure that transfers tokens between different blockchains by locking on one chain and minting a representation on another.
Token Standard
A specification defining how tokens are created, transferred, and managed on a blockchain platform.
Token Vesting
A schedule that gradually releases tokens to team members, investors, or contributors over time, preventing immediate market dumps.
Tokenization (Payments)
Replacing sensitive card numbers with non-sensitive tokens to reduce fraud risk and PCI compliance burden.
Tor and Bitcoin
Using the Tor anonymity network to hide a Bitcoin node's IP address, improving privacy but introducing potential attack vectors.
Trampoline Payments
A Lightning Network routing technique where lightweight clients delegate pathfinding to intermediate nodes, enabling mobile wallets to send payments without maintaining full network state.
Transaction ID (txid)
A unique 256-bit hash identifying a Bitcoin transaction, computed from the serialized transaction data.
Transaction Malleability
The ability to modify a Bitcoin transaction's ID without invalidating it, a critical bug that SegWit fixed to enable Lightning.
Transaction Monitoring
Automated surveillance of financial transactions to detect suspicious patterns indicating money laundering, fraud, or sanctions violations.
Transaction Pinning
Transaction pinning is a mempool attack where an adversary prevents a legitimate transaction from being fee-bumped or confirmed.
Transfer Restriction
Smart contract rules that limit who can send or receive a token, used for compliance in regulated stablecoins and securities.
Trusted Execution Environment (TEE)
An isolated processing environment within a CPU that protects code and data from the main operating system and other applications.
Trustless
Systems that operate through cryptographic verification rather than relying on trusted third parties.
TUSD (TrueUSD)
A fiat-backed stablecoin with real-time attestations of reserves, which faced controversy over its reserve management practices.
TVL (Total Value Locked)
The total value of crypto assets deposited in a DeFi protocol, the most common (but imperfect) metric for DeFi adoption.
UPI (Unified Payments Interface)
India's real-time mobile payment system processing billions of transactions monthly through interoperable bank-linked apps.
USDB Stablecoin
A Bitcoin-native stablecoin built on Spark that pays yield to holders, issued by Flashnet and backed by dollar-denominated reserves.
USDC (USD Coin)
A regulated dollar-backed stablecoin issued by Circle, fully reserved with cash and US Treasuries, available on multiple blockchains.
USDP (Pax Dollar)
A regulated dollar stablecoin issued by Paxos Trust Company, backed by cash and US Treasuries under New York banking supervision.
USDT (Tether)
The largest stablecoin by market cap, issued by Tether Limited, widely used in trading and emerging market payments.
UST Collapse (Terra/Luna)
The catastrophic failure of Terra's algorithmic stablecoin in May 2022, wiping out $40B+ and triggering industry-wide contagion.
Utreexo
Utreexo is a hash-based accumulator that compresses the Bitcoin UTXO set into a compact cryptographic proof, reducing node storage needs.
UTXO (Unspent Transaction Output)
The fundamental unit of Bitcoin ownership, representing an unspent output from a previous transaction that can be used as input to a new transaction.
UTXO Consolidation
Combining many small UTXOs into fewer larger ones during low-fee periods to reduce future transaction costs.
UTXO Set
The complete collection of all unspent transaction outputs on Bitcoin, representing the current state of who owns what.
Validity Proof
A cryptographic proof submitted to the base layer that proves a batch of L2 transactions was executed correctly, enabling ZK rollups.
Validium
A Layer 2 design using validity proofs like ZK rollups but storing data off-chain, trading security for lower costs.
Velocity Check
A fraud detection rule that flags or blocks transactions when a user exceeds a threshold of attempts within a time window.
Virtual Bytes (vBytes)
The weight-adjusted size metric for Bitcoin transactions, determining fees under the SegWit weight system.
Virtual Card
A digitally-generated payment card number used for online or in-app transactions without requiring a physical plastic card.
Watch-Only Wallet
A wallet that can view balances and generate addresses but cannot sign transactions, used for monitoring without key exposure.
Watchtower
An outsourced monitoring service that watches for channel breaches on the Lightning Network and broadcasts penalty transactions to protect users who are offline.
Weight Units (WU)
Weight units are the SegWit measurement system for Bitcoin transaction size, with blocks limited to 4 million WU.
Whitepaper
A whitepaper is a technical document describing the design, purpose, and mechanics of a blockchain protocol or cryptocurrency project.
Wire Transfer
An electronic funds transfer between banks that settles individually and typically same-day, used for large or urgent payments.
Witness Data
The segregated signature and script data in SegWit transactions, stored separately from the main transaction structure.
Wrapped Asset
A token on one blockchain that represents an asset from another chain, typically held by a custodian or smart contract.
Wrapped Bitcoin (WBTC)
An ERC-20 token on Ethereum backed 1:1 by Bitcoin held in custody, enabling Bitcoin to participate in Ethereum DeFi.
Wumbo Channel
A Lightning channel exceeding the default 0.1677 BTC capacity limit, enabled by both peers advertising wumbo feature support.
Zero-Conf Channels
Lightning channels that can be used immediately before the funding transaction confirms on-chain, accepting temporary trust tradeoffs.
Zero-Knowledge Proof (ZKP)
A cryptographic method allowing one party to prove they know something without revealing the underlying information.
ZK Rollup
A Layer 2 scaling solution that uses zero-knowledge proofs to verify off-chain computation, enabling instant finality withdrawals.
zk-SNARK
Zero-Knowledge Succinct Non-Interactive Argument of Knowledge: compact proofs verifiable in milliseconds without interaction.
zk-STARK
Zero-Knowledge Scalable Transparent Argument of Knowledge: post-quantum proofs with no trusted setup but larger proof sizes.