RIPEMD-160 48-bit-prefix collision

Result

collision.json supplies two distinct eight-byte hexadecimal inputs. Their RIPEMD-160 digests share the first 48 most-significant bits:

Input	Full RIPEMD-160 digest	First 48 bits
0x00694f1100694f11	143d753a248c61ddaaabac6163d0bc6ced16da5d	143d753a248c
0x00a181a600a181a6	143d753a248c0825fe2ee2da177b0b83184c2faf	143d753a248c

Evidence and method

Fact: the inputs, full digests, and prefixes in the table were recomputed locally with Node.js crypto.createHash('ripemd160'). The same result can be checked with OpenSSL 3.0.2 using openssl dgst -ripemd160 on the raw bytes.

Fact: find_collision.js enumerated eight-byte inputs consisting of the big-endian 32-bit counter repeated twice, calculated RIPEMD-160 for each, and stored the first 48 digest bits in an in-memory hash table. It found this pair while enumerating counters through 10,584,486. The search output reported the common prefix 143d753a248c and counters 6901521 and 10584486.

Inference: since the first six digest bytes are equal and the byte strings are different, this is a collision under the requested 48-bit MSB truncation.

Limits and unanswered questions

Fact: the full 160-bit digests differ, so this report does not claim a full-RIPEMD-160 collision. No assertion is made about collision resistance at other truncation lengths, alternative input encodings, or other hash functions. The final verifier remains responsible for its independent recomputation.