HMAC Generator

Category: Hash & MAC & CRC · Node Type ID: mac-hmac

Hash-based Message Authentication Code (RFC 2104)

Overview

Computes a Hash-based Message Authentication Code (HMAC, RFC 2104 / FIPS 198-1) over an input message using a secret key and a selected underlying cryptographic hash function (SHA-256, SHA-384, SHA-512, SHA3-256, or SHA-1).

HMAC provides both data integrity and authenticity verification for parties sharing a secret key. Keys of any non-zero byte length are accepted (keys longer than the hash block size are hashed first; shorter keys are zero-padded to the block size per RFC 2104).

When to Use

Authenticating API payloads, webhook requests, JWT HS256/HS384/HS512 tokens, or encrypt-then-MAC ciphertexts.
Building custom key-derivation or challenge-response protocols.

Parameter Configuration

Parameter (ID)	Type & Default	Visibility Condition	Description & Options
Hash Algorithm `algorithm`	`select` Default: `SHA-256`	Always visible	Selects the underlying hash function and resulting MAC tag length: `SHA-256` (32B), `SHA-384` (48B), `SHA-512` (64B), `SHA3-256` (32B), or `SHA-1` (20B). `SHA-256`: SHA-256 `SHA-512`: SHA-512 `SHA3-256`: SHA3-256

Port I/O Specification

See Ports & Connections for general wiring rules, data type colors, and dynamic port creation.

Input Ports

Port Nature: Fixed Input Ports (2 total).

Port Name	Port ID	Data Type	Required	Visibility Condition	Description
`Secret Key`	`key`	`Bytes`	Required	Always visible	Secret HMAC key (`Uint8Array`; must be at least 1 byte).
`Message`	`data`	`Bytes`	Required	Always visible	Message payload (`Uint8Array`) to authenticate.

Output Ports

Port Nature: Fixed Output Ports (1 total).

Port Name	Port ID	Data Type	Visibility Condition	Description
`MAC Digest`	`mac`	`Bytes`	Always visible	Computed HMAC authentication tag (`Uint8Array`).

Error Cases

This node has no runtime failure cases (errorProfile: none) and always succeeds for any valid typed input.

Examples

Computing and Verifying an HMAC-SHA256 Tag

Generate a 32-byte HMAC tag and compare it against an expected tag.

Connect your secret key to Secret Key and payload bytes to Message with Hash Algorithm set to HMAC-SHA256 (32 Bytes).
Connect the MAC Tag output to Operand A of a Compare node to verify against an expected MAC.