`hashlib` — cryptographic hashes

import hashlib

This port ships SHA-256, SHA-1, and MD5, all backed by the same axtls implementations used by ssl and _ssh. Real implementations — not stubs.

Common API

All three hash objects follow the same shape:

h = hashlib.sha256()        # constructor (also: .sha1(), .md5())
h.update(b'hello')          # absorb more bytes
h.update(b' world')
h.digest()                  # b'<raw 32 bytes for sha256>'
h.hexdigest()               # '<lowercase hex string>'

Optionally pass initial data:

h = hashlib.sha256(b'hello world')
h.hexdigest()
# 'b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9'

Examples

Hash a file in chunks

def file_sha256(path):
    h = hashlib.sha256()
    with open(path, 'rb') as f:
        while True:
            chunk = f.read(4096)
            if not chunk:
                break
            h.update(chunk)
    return h.hexdigest()

print(file_sha256('MP.EXE'))

HMAC (no `hmac` module, but you can DIY)

def hmac_sha256(key, msg):
    block_size = 64
    if len(key) > block_size:
        key = hashlib.sha256(key).digest()
    key = key + b'\x00' * (block_size - len(key))
    o_pad = bytes(b ^ 0x5C for b in key)
    i_pad = bytes(b ^ 0x36 for b in key)
    inner = hashlib.sha256(i_pad + msg).digest()
    return hashlib.sha256(o_pad + inner).hexdigest()

print(hmac_sha256(b'secret', b'message'))

(The lower-level _libssh2_axtls_hmac API used internally by SSL/SSH already does this; the Python hmac module isn’t bundled, but the above 8-liner is enough.)

NOT included

These upstream Python algorithms aren’t built into this port:

sha224, sha384, sha512 — backend supports them but not enabled by default
sha3_* — not bundled
blake2b, blake2s — not bundled

If you need them, the axtls SHA-384/512 implementations are already linked in (used by SSH); enabling the Python wrapper is a small port change.

Credit: api shape from MicroPython hashlib docs (MIT).

hashlib — cryptographic hashes