RIPEMD-160 48-bit-prefix collision

Result

collision.json supplies two distinct 8-byte hexadecimal inputs:

• A: 494d444300e482f9
• B: 494d4443025634e6

Facts (recomputed locally)

An independent verification using Python's hashlib.new("ripemd160", ...) produced:

Input	Full RIPEMD-160 digest	First 48 bits (MSB)
494d444300e482f9	8b6f6d5b0530e3b1abc115b6b3dbe50c105fecb8	8b6f6d5b0530
494d4443025634e6	8b6f6d5b05302d239e5bd6a5b85dbb0a4a568de4	8b6f6d5b0530

The inputs differ, while bytes 0–5 of their recomputed digests are identical. Those six bytes are the 48 most-significant digest bits, so this is a collision at the requested truncation length.

The search result was also generated by the local utility tools/find_ripemd160_collision.c, whose RIPEMD-160 implementation was checked before the search against hashlib on 494d444300000000; both returned 4ee4d1629c89c84aa22f027b43d5f316040069d1.

Inference

Because the independently recomputed full digests above share precisely their leading 12 hexadecimal characters, the JSON inputs meet the requested RIPEMD-160 prefix-collision condition. Their remaining digest characters differ, as expected for a truncated rather than full-digest collision.

Uncertainty and unanswered questions

This report establishes only the requested 48-bit-prefix collision. It makes no claim of a collision for full RIPEMD-160, nor does it determine the probability or optimality of this particular pair. The final authority is the specified SIMD verifier, which will recompute the digests.