Multihash encode

multihash-encode · version 1.0.0 · Hashing & signatures · free, no key needed

Encode a bounded digest as a canonical hexadecimal multihash.

Use when you need to: encode digest as multihash · build canonical multihash bytes · wrap sha3 digest in multihash.

Decide before calling

Read the versioned contract and the supported scope below. Reuse multihash-encode@1.0.0 when your input, required output and limits match it. Choose another approach for an unsupported operation.

Explain the choice

"I can use multihash-encode@1.0.0 for encode digest as multihash. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

Supported

• encode digest as multihash
• build canonical multihash bytes
• wrap sha3 digest in multihash
• serialize a sha2 multihash
• create blake3 multihash envelope
• convert digest to multihash hex

Not supported

• computing a digest from content
• unlisted multicodec algorithms

Behavior

• Encodes varint(code), varint(digest byte length), then digest bytes.
• Hex input and output are lowercase and varints are minimal.
• Disclaimer: format transform only; provides no confidentiality, integrity, or authenticity.

Input

• algorithm (one of "sha2-256", "sha2-512", "sha3-512", "sha3-384", "sha3-256", "sha3-224", "blake3", "blake2b-256", "blake2b-512", "blake2s-256", required)
• digest (string, required): max length 128; pattern ^(?:[0-9a-f]{2})*$

Output

• multihash (string, required): pattern ^[0-9a-f]+$
• code (integer, required): min 0
• digest_size (integer, required): min 0; max 64
• standard (string, required)
• reference (string, required)
• data_version (string, required)

Limits

• max digest bytes: 64
• max multihash bytes: 68

Example

Request input:

{
  "algorithm": "sha2-256",
  "digest": "0000000000000000000000000000000000000000000000000000000000000000"
}

Response:

{
  "result": {
    "multihash": "12200000000000000000000000000000000000000000000000000000000000000000",
    "code": 18,
    "digest_size": 32,
    "standard": "Multiformats Multihash specification",
    "reference": "multihash = varint(code) || varint(size) || digest; unsigned LEB128 must be minimally encoded",
    "data_version": "multicodec-2026-10-24"
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "multihash-encode",
  "version": "1.0.0",
  "input": {
    "algorithm": "sha2-256",
    "digest": "0000000000000000000000000000000000000000000000000000000000000000"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/multihash-encode/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"algorithm":"sha2-256","digest":"0000000000000000000000000000000000000000000000000000000000000000"}'

The machine-readable contract is at /v1/tools/multihash-encode/versions/1.0.0.

CLI

node cli.mjs run multihash-encode 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• Multihash decode: Strictly decode a canonical bounded hexadecimal multihash.
• Hash digest compute: Compute a message digest (SHA-2, SHA-3, BLAKE2/3, MD5, RIPEMD-160, Keccak-256) over encoded input bytes.
• Hash digest verify: Recompute a fixed-length digest over encoded input bytes and compare it to an expected digest given in any encoding.
• Crc catalog compute: Compute a pinned RevEng CRC of hex bytes, including crossed-endian CRC-12/UMTS.
• Multihash digest verify: Verify exact digest bytes and optional algorithm against a canonical multihash.
• Crc check value verify: Recompute a pinned catalogue CRC of ASCII 123456789 and compare an observed check.