salt the pkware encryption header per entry in _zip_entry_open#444
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kuba-- merged 2 commits intoJul 18, 2026
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kuba--
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| (mz_uint8)((mz_crc32(MZ_CRC32_INIT, enc_header, i) ^ salt) >> | ||
| (i & 7)); | ||
| enc_header[i] = zip_pkware_encrypt_byte(&zip->entry.enc_keys, rnd); | ||
| salt = salt * 1103515245u + 12345u; |
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- Comment + #define naming the LCG.
- Simpler mix:
salt = (salt << 5) ^ (salt >> 7) ^ (mz_uint32)i
— also fine for uniqueness.
True random for the 11 bytes — better hygiene, more platform work.
- (Optionally): True random for the 11 bytes — better hygiene, more platform work.
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switched to your shift/xor mix, so the lcg constants are gone and the comment now describes the stir instead. left true random out for now to keep it portable, happy to follow up with it if you want. full suite still passes, including the determinism test.
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Jul 18, 2026
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encryption header is identical for every entry under the same password
The header's first 11 bytes came from a crc of the bytes written so far, which depends only on the password, so identical plaintext encrypted to identical ciphertext and entries reused the keystream. Salted the derivation with the entry's own local-header offset and time so each entry gets a distinct header; encrypt and decrypt stay symmetric so existing archives still read back.