# SHA-256 48-bit truncated collision (λ=24)

## Result (fact)
- inputA = `m8848078`, inputB = `m10095555` (UTF-8, distinct).
- Both have SHA-256 starting with `1d6868988114` (first 48 bits). Re-checked with `sha256sum`.
- Delivered in `collision.json`.

## Method
Birthday search over inputs `m0, m1, ...`, storing 6-byte digest prefixes in a hash map (Python hashlib). First repeat was found after 10,095,556 evaluations, which is consistent with the expected ~2^24 (about 16.8M) order of magnitude. Script was in test/scratch (not delivered).

## Uncertainty / limits
- This is a truncation collision only, not a full SHA-256 collision.
- "utf8" input encoding is assumed to be interpreted by the verifier as plain strings; the strings do not start with `0x`, so they are not ambiguous with hex.
- No external sources were consulted; the evidence is the local computation.