RIPEMD-160 collision at 48 bits

The requested collision is in collision.json. Its input strings use 0x hex notation and represent raw bytes, not the literal ASCII hex strings.

Computed evidence

Input	Full RIPEMD-160 digest
0x19bef10000000000	902e5fc86be47b1e2a17de2aab65d4e765623a05
0x1022730100000000	902e5fc86be4a99253faddc650510cb85e77233d

Both digests have the same first six bytes, 902e5fc86be4, which are the first 48 bits in MSB order. The inputs are distinct, and the full digests differ. This satisfies the requested truncation with lambda = 24.

Evidence is attributable to local execution of find_collision.c, which searched successive eight-byte little-endian integer encodings using OpenSSL's RIPEMD160 function. It found indices 15,842,841 and 24,322,576 after 24,322,577 evaluations.

The saved JSON was then checked by verify_collision.py. That script parsed the exact fields, decoded the input bytes, checked distinctness, recomputed full digests with Python hashlib, checked those against openssl dgst -ripemd160 -binary, and asserted equality of the first six digest bytes. The check passed. The local OpenSSL version was 3.0.13.

Limits

These are directly computed local results, not an independently certified SIMD verification. Python and the command-line checks may share the same underlying OpenSSL implementation; they are separate execution paths, not independent cryptographic implementations. No SIMD verifier was available or run here. There is no inference that the full 160-bit digests collide, and no claim about collision resistance beyond this specific 48-bit example. Acceptance by the external SIMD verifier remains unobserved.