Glossary

Term	Simple meaning
Account-linking ID / `account_linking_id`	Opaque ID returned after Account Linking. Debit Authorization sends it to identify which active account link this authorization belongs to.
Acquiring institution	The financial institution that receives and posts money for the beneficiary or creditor.
AES-256-GCM	The encryption method used for message plaintext. AES uses a 256-bit key; GCM also detects tampering.
Authentication actor	The person or system that performed authentication. The documented device-local flow uses `CUSTOMER`.
Authentication binding	Values that connect an authentication claim to one registered authenticator and its protected hardware.
Authentication context	Where the authentication decision happened, such as locally on the customer's registered device.
Authentication type	The method actually used, such as strong device biometric authentication.
Authenticator ID / `key_id`	Positive numeric database ID of the active authenticator used for approval. It is not a cryptographic key, device ID, GUID, or quoted string.
Base64	Text encoding used to carry binary signatures and public keys safely in JSON or headers. It is encoding, not encryption.
Beneficiary	Person or organisation whose account receives a credit.
BIC / `BICFI`	Bank Identifier Code for a financial institution. It is used only where the agreed routing setup requires it.
Blinc	The payment network participant that sends the documented requests to institution-provided endpoints.
Booking date/time	When an entry is recorded in an account ledger.
Business rejection	A protected response saying the requested financial action was not accepted, commonly `RJCT`. It can be carried in HTTP `200`.
BVN	Bank Verification Number, an identity scheme used in Nigerian financial services. Treat the value as sensitive.
Ciphertext	Encrypted bytes that cannot be read without the receiver private key and derived AES key.
Clearing channel	The route used to exchange and settle an instruction, for example `RTNS`.
Clearing-system reference	Opaque reference used to trace a transaction in the clearing or switching system.
Creditor	Person or organisation entitled to receive money. In the examples, the creditor is Example Store.
Credit Notification	Message reporting that a beneficiary credit entry is pending or booked. It does not instruct a second credit.
Credit Transfer	Instruction to credit one beneficiary account.
Customer-device signature	Signature created by the customer's registered device over the customer-visible transaction facts. It is separate from the institutional signature.
Date-time	UTC instant written as `yyyy-MM-ddTHH:mm:ss.fffZ`, for example `2026-08-16T10:15:30.123Z`.
Debtor	Person or organisation whose account supplies the money.
Debit Authorization	Request asking the issuing institution to approve and record one debit against a previously linked account.
ECDH	Elliptic Curve Diffie-Hellman, used by sender and receiver keys to derive the same secret without transmitting that secret.
ECDSA	Elliptic Curve Digital Signature Algorithm, used to sign and verify the exact plaintext.
Encryption envelope	The outer JSON `encrypteddata` object containing algorithm, ephemeral public key, and ciphertext. It does not contain the institutional signature.
End-to-end ID	Opaque business reference that follows one payment across participating systems.
Ephemeral public key	One-use public key generated for one encrypted message. It is not the sender's long-term identity key.
Financial institution	Regulated participant that provides the endpoints described by this contract. After first mention, the guides use `institution`.
Hexadecimal / hex	Text representation using digits `0-9` and letters `A-F`. The encrypted ciphertext-and-tag value uses uppercase hex.
HKDF-SHA256	Key derivation function that turns the ECDH secret into the AES key and nonce using SHA-256.
HTTP status	Transport-level result such as `200`, `400`, or `500`. It does not replace the decrypted business status.
HTTPS	HTTP protected by TLS while the request travels over the network. Message encryption and signatures still apply.
Idempotency	Processing the same business request more than once has the same result and creates no duplicate financial action.
Institution member code	Six-digit routing code that Blinc issues to a participating institution during onboarding. The institution must not create its own code.
Institutional signature	ECDSA signature in `x-signature` proving who sent the exact plaintext and that it did not change.
Instruction ID	Opaque ID for one payment instruction. Keep it unchanged when Blinc retries Credit Notification, Credit Transfer, or Reverse. After a Debit Authorization timeout, the original debit identifiers are used by Reverse; the debit is not resent.
ISO 20022	Financial-message naming and structure standard that inspires names such as `GrpHdr`, `PmtId`, and `RmtInf`.
Issuing institution	Institution that services the customer's/debtor's account and decides whether to accept linking, unlinking, debit, and reversal requests.
Account link	Institution-stored record that connects a customer account to a creditor and records the permitted debit relationship.
Account link ID	Opaque ID created by the issuing institution after Account Linking and required for later unlink requests. Debit Authorization refers to it as `account_linking_id`.
Message ID / `GrpHdr.MsgId`	Structured 35-digit ID for one message: six-digit sender code, 17-digit UTC timestamp, and 12-digit sequence.
NUBAN	Nigerian Uniform Bank Account Number scheme. Treat account numbers as sensitive.
Opaque ID	Identifier that must be stored and compared as a complete value rather than parsed for hidden meaning.
P-256	Elliptic curve used for ECDH key agreement and ECDSA signatures.
Plaintext	Readable compact JSON before encryption or after successful decryption. The institutional signature covers its exact representation.
Private key	Secret half of a key pair. It never leaves its owner's controlled key store.
Public key	Shareable half of a key pair, used to encrypt for its owner or verify signatures created by the matching private key.
Replay	Reuse of an earlier valid protected delivery. Timestamp and replay storage prevent it from causing another action.
Reversal	Request to return the full amount of an accepted debit.
RFC 3339 / ISO 8601	Date-time text standards used for unambiguous UTC values.
Remittance information	Narration or invoice details explaining why money moved.
SHA-256	Hash function used by ECDSA and HKDF in this contract.
Signature header	`x-signature`; contains the Base64 institutional signature of the exact plaintext.
Settlement amount	Amount exchanged between participating institutions. It can differ from the instructed amount only when contracted charge or foreign-exchange rules permit it.
Settlement date/time	UTC value saying when inter-institution settlement applies.
Timestamp header	`x-timestamp`; UTC time the protected HTTP delivery was created, used for freshness and replay checks.
Transaction ID	Opaque ID for one transaction in the switching flow.
UTC	Coordinated Universal Time. A trailing `Z` marks a UTC date-time.
Value date/time	When credited funds begin to have value according to ledger rules; it can differ from booking time.

Common status codes

Code	Meaning
`ACSC`	Accepted and recorded/settled as required by the operation.
`RJCT`	Rejected; read the reason object.
`PDNG`	Pending; processing is not final.
`BOOK`	Credit Notification entry is booked.
`CRDT`	The notified ledger entry is a credit.

See errors and retries for rejection reason codes and corrective actions.

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Common status codes

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