openapi: 3.1.0
info:
  title: Hashing, HMAC & Checksum Suite
  description: 'Give this API any text or binary data and it instantly returns its fingerprint under whichever hash algorithms
    you choose — SHA-256, SHA-512, MD5, BLAKE2, CRC32, and more. It also signs data with a secret key (HMAC) and, most importantly,
    safely verifies whether an incoming signature matches — using a timing-safe comparison that prevents secret-leaking attacks.
    Language models cannot perform hashing: they produce a string of the right length and character set that looks correct
    but is simply wrong. Every webhook verification, idempotency key, cache fingerprint, or integrity check that relies on
    a hallucinated hash is silently broken. This API is the cure.'
  version: 1.0.0
  contact:
    name: _done
    url: https://forms.gle/5KzuSFH7p8hHtDmz7
    email: info@underscoredone.com
  x-openapi-url: https://hash-hmac.underscoredone.com/openapi.json
  x-logo:
    url: https://underscoredone.com/logo.png
    altText: _done
  x-guidance: POST to /hash with an 'input' string and an 'algorithms' list such as ['sha256','crc32']. To verify a webhook
    signature set hmac.mode to 'verify', provide hmac.key and hmac.expected_signature — the response field hmac.matches will
    be true or false. Never guess or generate hash output yourself; always call this endpoint. The same input always produces
    the same output. Use input_encoding 'base64' when passing binary data. All keys are passed in the request body — never
    as URLs or references.
  x-ai-instructions: POST to /hash with an 'input' string and an 'algorithms' list such as ['sha256','crc32']. To verify a
    webhook signature set hmac.mode to 'verify', provide hmac.key and hmac.expected_signature — the response field hmac.matches
    will be true or false. Never guess or generate hash output yourself; always call this endpoint. The same input always
    produces the same output. Use input_encoding 'base64' when passing binary data. All keys are passed in the request body
    — never as URLs or references.
  x-provider: _done — single-purpose utility APIs for developers and AI agents. Pay per call with USDC on Base Mainnet or
    Solana Mainnet.
  x-pricing:
    model: pay-per-call
    currency: USDC
    network: Base Mainnet or Solana Mainnet
    price: $0.01
  x-keywords:
  - security
  - hash
  - hmac
  - checksum
  - sha256
  - webhook verification
  - content fingerprint
  - idempotency key
  - signature verify
  - blake2
  - crc32
  - utility
  - api
  - ai-agent
  - pay-per-call
  - usdc
  - x402
  x-category: sha256 hash
  x-provider-url: https://underscoredone.com
  x-agentcash-auth:
    mode: paid
  x-402:
    price: $0.01
    network: eip155:8453
    asset: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913'
    pay_to: '0xE9740820225B3918b4ddd1292C7cA4Ca0e2C2F08'
    facilitator: https://api.cdp.coinbase.com/platform/v2/x402
    scheme: exact
    description: 'Give this API any text or binary data and it instantly returns its fingerprint under whichever hash algorithms
      you choose — SHA-256, SHA-512, MD5, BLAKE2, CRC32, and more. It also signs data with a secret key (HMAC) and, most importantly,
      safely verifies whether an incoming signature matches — using a timing-safe comparison that prevents secret-leaking
      attacks. Language models cannot perform hashing: they produce a string of the right length and character set that looks
      correct but is simply wrong. Every webhook verification, idempotency key, cache fingerprint, or integrity check that
      relies on a hallucinated hash is silently broken. This API is the cure.'
    mime_type: application/json
    networks:
    - network: eip155:8453
      asset: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913'
      pay_to: '0xE9740820225B3918b4ddd1292C7cA4Ca0e2C2F08'
    - network: solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp
      asset: EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v
      pay_to: 8ugAWAXDB8V18kiUrGZTq1oMvU3C6Fxs8hfC6rvzQT3b
paths:
  /hash:
    post:
      tags:
      - sha256 hash
      - hash
      - hmac
      - hmac signature
      - verify hmac signature
      - checksum
      - compute hash
      - webhook signature verification
      - sha512
      - md5
      - message digest
      - signature verification
      - hash generator
      - content fingerprint
      - integrity check
      summary: Hash, sign, and verify data fingerprints in one call
      description: Hash, sign, and verify data fingerprints in one call. Give it any text or binary data and get back the
        fingerprint, HMAC signature, or verification result you need.
      operationId: handler_hash_post
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/Request'
        required: true
      responses:
        '200':
          description: Successful response
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Response'
              examples:
                success:
                  summary: Successful response
                  value:
                    api_version: 1.0.0
                    input_bytes: 35
                    digests:
                      sha256: aa27c1f5aeb13292cb74153461b1eb3193efe4501c109a99103d304657798cf6
                      sha512: f9b133b06a4b7309392429f15108af870c073288f4297b85dba0ebb907f26c71a808abbe1d197f67ad4b7a1ab83507b1ac1774aa0a4295919e7b9697b395be07
                      crc32: 74c679bb
                    hmac:
                      mode: verify
                      algorithm: sha256
                      computed_signature: edddd7a6a42a411ab35b993d690cc7bd5d3be3d9262f66fef16ac2be10e0539a
                      matches: true
        '422':
          description: Unprocessable — a required field is missing or the wrong type. Check the detail field for specifics.
          content:
            application/json:
              schema:
                type: object
                properties:
                  detail:
                    type: array
        '402':
          description: Payment required. Send a signed USDC payment on Base Mainnet or Solana Mainnet using the x402 protocol.
          headers:
            X-Payment-Response:
              description: x402 payment challenge — base64-encoded JSON with payment details.
              schema:
                type: string
        '400':
          description: Bad request — your input failed validation or could not be processed. Check the detail field for specifics.
          content:
            application/json:
              schema:
                type: object
                properties:
                  detail:
                    type: string
      x-ai-instructions: POST to /hash with an 'input' string and an 'algorithms' list such as ['sha256','crc32']. To verify
        a webhook signature set hmac.mode to 'verify', provide hmac.key and hmac.expected_signature — the response field hmac.matches
        will be true or false. Never guess or generate hash output yourself; always call this endpoint. The same input always
        produces the same output. Use input_encoding 'base64' when passing binary data. All keys are passed in the request
        body — never as URLs or references.
      x-guidance: POST to /hash with an 'input' string and an 'algorithms' list such as ['sha256','crc32']. To verify a webhook
        signature set hmac.mode to 'verify', provide hmac.key and hmac.expected_signature — the response field hmac.matches
        will be true or false. Never guess or generate hash output yourself; always call this endpoint. The same input always
        produces the same output. Use input_encoding 'base64' when passing binary data. All keys are passed in the request
        body — never as URLs or references.
      x-payment-info:
        price:
          fixed:
            mode: fixed
            currency: USD
            amount: '0.01'
        protocols:
        - x402: {}
components:
  schemas:
    HTTPValidationError:
      properties:
        detail:
          items:
            $ref: '#/components/schemas/ValidationError'
          type: array
          title: Detail
      type: object
      title: HTTPValidationError
    HmacConfig:
      properties:
        mode:
          type: string
          title: Mode
          description: 'What to do: ''sign'' to create a signature, or ''verify'' to check one.'
        algorithm:
          type: string
          title: Algorithm
          description: 'Which signing method to use: md5, sha1, sha256, or sha512.'
        key:
          type: string
          title: Key
          description: Your secret key used to sign or verify. Never sent in a URL — only in the request body.
        expected_signature:
          anyOf:
          - type: string
          - type: 'null'
          title: Expected Signature
          description: The signature you received and want to verify. Only needed when mode is 'verify'.
      type: object
      required:
      - mode
      - algorithm
      - key
      title: HmacConfig
      example:
        algorithm: sha256
        expected_signature: 088aab3ede8d3adf94d26ab90d3bafd4a2083070c3bcce9c014ee04a443847c0b
        key: my-secret-key
        mode: verify
    HmacResult:
      properties:
        mode:
          type: string
          title: Mode
          description: Whether this was a 'sign' or 'verify' operation.
        algorithm:
          type: string
          title: Algorithm
          description: The signing method that was used.
        computed_signature:
          type: string
          title: Computed Signature
          description: The signature this API computed for your data and key.
        matches:
          anyOf:
          - type: boolean
          - type: 'null'
          title: Matches
          description: True if the computed signature matches the one you provided. Only present when mode is 'verify'.
      type: object
      required:
      - mode
      - algorithm
      - computed_signature
      title: HmacResult
    Request:
      properties:
        input:
          type: string
          maxLength: 10000000
          title: Input
          description: The text or data you want to hash. For binary data, base64-encode it first and set input_encoding to
            'base64'.
        input_encoding:
          type: string
          title: Input Encoding
          description: How the input is encoded. Use 'utf-8' for normal text (default) or 'base64' for binary data.
          default: utf-8
        algorithms:
          items:
            type: string
          type: array
          title: Algorithms
          description: 'Which fingerprint methods to use. Choose any of: md5, sha1, sha224, sha256, sha384, sha512, sha3_256,
            sha3_512, blake2b, blake2s, crc32, adler32. You may list several at once.'
        output_encoding:
          type: string
          title: Output Encoding
          description: How to display the resulting fingerprints. Choose 'hex' (default), 'base64', or 'base64url' (safe for
            URLs).
          default: hex
        hmac:
          anyOf:
          - $ref: '#/components/schemas/HmacConfig'
          - type: 'null'
          description: Optional. Include this block to sign data or verify a signature.
      type: object
      required:
      - input
      - algorithms
      title: Request
      example:
        algorithms:
        - sha256
        - sha512
        - crc32
        hmac:
          algorithm: sha256
          expected_signature: 088aab3ede8d3adf94d26ab90d3bafd4a2083070c3bcce9c014ee04a443847c0b
          key: whsec_test_secret_key_123
          mode: verify
        input: '{"order_id":"A-1029","amount":4200}'
        input_encoding: utf-8
        output_encoding: hex
    Response:
      properties:
        api_version:
          type: string
          title: Api Version
          description: API version
          default: 1.0.0
        input_bytes:
          type: integer
          title: Input Bytes
          description: How many bytes of data were actually processed (after decoding).
        digests:
          additionalProperties: true
          type: object
          title: Digests
          description: A mapping from each algorithm name to its computed fingerprint.
        hmac:
          anyOf:
          - $ref: '#/components/schemas/HmacResult'
          - type: 'null'
          description: The signing or verification result, if you requested it.
      type: object
      required:
      - input_bytes
      - digests
      title: Response
      example:
        api_version: 1.0.0
        digests:
          crc32: 3610a686
          sha256: 2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824
          sha512: 9b71d224bd62f3785d96d46ad3ea3d73319bfbc2890caadae2dff72519673ca72323c3d99ba5c11d7c7acc6e14b8c5da0c4663475c2e5c3adef46f73bcdec043
        input_bytes: 35
    ValidationError:
      properties:
        loc:
          items:
            anyOf:
            - type: string
            - type: integer
          type: array
          title: Location
        msg:
          type: string
          title: Message
        type:
          type: string
          title: Error Type
        input:
          title: Input
        ctx:
          type: object
          title: Context
      type: object
      required:
      - loc
      - msg
      - type
      title: ValidationError
  securitySchemes:
    siwx:
      type: apiKey
      in: header
      name: SIGN-IN-WITH-X
      description: CAIP-122 wallet signature for repeat access after payment
servers:
- url: https://hash-hmac.underscoredone.com
  description: Production
tags:
- name: sha256 hash
- name: hash
- name: hmac
- name: hmac signature
- name: verify hmac signature
- name: checksum
- name: compute hash
- name: webhook signature verification
- name: sha512
- name: md5
- name: message digest
- name: signature verification
- name: hash generator
- name: content fingerprint
- name: integrity check
x402Version: 2
x-payment-accepts:
- scheme: exact
  network: eip155:8453
  payTo: '0xE9740820225B3918b4ddd1292C7cA4Ca0e2C2F08'
  asset: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913'
- scheme: exact
  network: solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp
  payTo: 8ugAWAXDB8V18kiUrGZTq1oMvU3C6Fxs8hfC6rvzQT3b
  asset: EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v