hash-collision · shipping · also Digest collision

Hash collision

A hash collision occurs when two distinct inputs produce the same digest under the same hash function and parameters.

Related Observatory article: Hash collision on hesela.com

Hashing identical bytes twice is not a collision. Finding any colliding pair differs from finding a replacement for an already specified original, which is a second-preimage problem. [1] [2] A stale or misplaced record with its own valid digest can pass a check without any collision. [5]

Relations

related

checksum, cryptographic-hash, merkle-tree, deduplication

Limitations

• Collision resistance concerns the difficulty of finding colliding inputs, not an assertion that every input has a unique digest. [3]
• CRC undetected-error probabilities require a stated error model and cannot be treated as universal device failure rates. [4]

Citations

1. NIST CSRC glossary: collision (accessed 2026-10-12)
2. NIST CSRC glossary: second preimage resistance (accessed 2026-10-12)
3. NIST CSRC glossary: cryptographic hash function and security properties (accessed 2026-10-12)
4. RFC 3385: iSCSI CRC/Checksum Considerations, sections 1-2 and 10 (historical error-model analysis) (accessed 2026-10-12)
5. Hesela: Why a valid checksum can still return the wrong data (accessed 2026-10-12)

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