SHA-256 collision for the first 48 bits

The requested collision is provided in collision.json. Both inputs are literal UTF-8 strings, with no trailing newline:

• inputA: identitymd-sha256-48-33470631
• inputB: identitymd-sha256-48-39003384

Observed evidence

Input	Full SHA-256 digest
inputA	52b3d5bed12ac4bf555f73aeccadf4ee8f59b69258cdc319faa44d33648c6cc0
inputB	52b3d5bed12ad36c1fe698be56d9f3e61098e9de3f5cf17c642a547907f1f4bf

The first 12 hexadecimal digits (six bytes, or 48 most significant bits) are identical: 52b3d5bed12a. The inputs are distinct, and their full digests differ.

These values were computed locally using Python's hashlib.sha256 and confirmed using the OpenSSL 3.0.2 command line tool. The machine-readable Python check is saved in verification.json; its source is tools/verify_collision.py.

Reproduce the check from the repository root, without network access:

python3 tools/verify_collision.py
printf %s identitymd-sha256-48-33470631 | openssl dgst -sha256
printf %s identitymd-sha256-48-39003384 | openssl dgst -sha256

Search and conclusion

tools/search_collision.py enumerated strings of the form identitymd-sha256-48-N, starting at N=1, and stored each six-byte digest prefix until a duplicate appeared. The run found this pair at evaluation 39,003,384, after 99.620 seconds. Search timing is a local observation, not a performance guarantee. Rerunning the search requires several gigabytes of memory; checking the supplied pair does not.

The conclusion that this pair satisfies the requested 48-bit collision follows directly from the byte comparison. This is a truncated digest collision; it does not establish a collision in all 256 bits.

Limits and unanswered questions

All evidence here comes from local checks by the implementing agent. Python and the OpenSSL command line tool may use the same underlying cryptographic library, so they do not constitute independent implementation validation. The external SIMD verifier has not been run in this environment; its acceptance remains unobserved. No uncertainty remains in the locally observed equality of the six-byte prefixes.