RIPEMD-160 48-bit-prefix collision

Result

collision.json supplies two distinct byte strings, encoded as hexadecimal:

• inputA: 0x03c04551
• inputB: 0x03bf8869

Facts (locally recomputed)

The full RIPEMD-160 digests obtained during the final check were:

Input	RIPEMD-160 digest	First 48 bits (six MSB bytes)
03c04551	ba7d1fa52d960b0536516f56723ee28096ab6431	ba7d1fa52d96
03bf8869	ba7d1fa52d96e8504a06c29026c1568dba2704be	ba7d1fa52d96

The final verification was performed with this local computation:

python3 - <<'PY'
import hashlib
items = ['03c04551', '03bf8869']
prefixes = [hashlib.new('ripemd160', bytes.fromhex(x)).digest()[:6] for x in items]
assert items[0] != items[1]
assert prefixes[0] == prefixes[1]
PY

Inference

Because the inputs are distinct and the first six digest bytes are equal, this is a collision under the requested RIPEMD-160 truncation to 48 most-significant bits (lambda = 24). The complete 160-bit digests are not equal.

Uncertainty and unanswered questions

No claim is made about a collision for untruncated RIPEMD-160, nor about collision resistance at any other truncation length. Final acceptance remains dependent on the stated independent SIMD recomputation.