SHA-256 collision for the first 48 bits

The requested collision is delivered in collision.json, with algo set to sha256 and lambda set to 24. The 0x strings encode raw bytes, not literal UTF-8 text.

Input	Raw bytes (hex)	Full SHA-256 digest
A	e8f1380000000000	67171c0eb1922b1b1e7b76dd2213a661d3542f3c6b00e39279800abaaf50b502
B	23f68e0000000000	67171c0eb192a147eff93d18c3adf2a803bba554778ef76416669125a3a46e19

Both digests begin with 67171c0eb192: twelve hexadecimal digits, or 48 most-significant bits. The inputs are distinct eight-byte values. Their full digests differ.

Method and attributable evidence

A local C program enumerated integers starting at zero, encoded each integer as eight little-endian bytes, computed SHA-256 using OpenSSL, and stored the first six digest bytes in a hash table. It found the pair at integers 3,731,944 and 9,369,123 after 9,369,124 evaluations.

Python's hashlib.sha256 recomputed both full digests from the raw bytes. The OpenSSL 3.0.13 command-line tool separately recomputed both digests and matched Python's results. Assertions checked distinct inputs and equal 48-bit prefixes. These are locally observed results, not an independent review or a SIMD verifier verdict.

Reproduce the essential verification offline with Python 3:

import hashlib
import json
from pathlib import Path

p = json.loads(Path('collision.json').read_text())
assert set(p) == {'algo', 'lambda', 'inputA', 'inputB'}
assert p['algo'] == 'sha256' and p['lambda'] == 24
raw = [bytes.fromhex(p[k][2:]) for k in ('inputA', 'inputB')]
assert raw[0] != raw[1]
digests = [hashlib.sha256(x).hexdigest() for x in raw]
assert digests[0][:12] == digests[1][:12] == '67171c0eb192'
print(*digests, sep='\n')

Limits

The measured bytes and digests establish the truncated collision under hex decoding. No inference about a full 256-bit SHA-256 collision is made. The external SIMD verification has not been run here; its result remains unobserved. No network sources or external factual claims are needed for this direct computation.