64 lines
1.3 KiB
Markdown
64 lines
1.3 KiB
Markdown
File Format
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===========
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Header
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2 bytes header version (big endian uint16, currently 2)
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16 bytes file id
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Data block, default AES-GCM mode
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16 bytes GCM IV (nonce)
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1-4096 bytes encrypted data
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16 bytes GHASH
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Data block, AES-SIV mode (used in reverse mode, or when explicitly enabled with `-init -aessiv`)
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16 bytes nonce
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16 bytes SIV
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1-4096 bytes encrypted data
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Data block, XChaCha20-Poly1305 (enabled via `-init -xchacha`)
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24 bytes nonce
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1-4096 bytes encrypted data
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16 bytes Poly1305 tag
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Full block overhead (AES-GCM and AES-SIV mode) = 32/4096 = 1/128 = 0.78125 %
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Full block overhead (XChaCha20-Poly1305 mode) = 40/4096 = \~1 %
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Example: 1-byte file, AES-GCM and AES-SIV mode
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----------------------------------------------
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Header 18 bytes
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Data block 33 bytes
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Total: 51 bytes
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Example: 5000-byte file, , AES-GCM and AES-SIV mode
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---------------------------------------------------
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Header 18 bytes
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Data block 4128 bytes
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Data block 936 bytes
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Total: 5082 bytes
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Example: 1-byte file, XChaCha20-Poly1305 mode
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----------------------------------------------
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Header 18 bytes
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Data block 41 bytes
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Total: 59 bytes
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Example: 5000-byte file, XChaCha20-Poly1305 mode
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----------------------------------------------
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Header 18 bytes
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Data block 4136 bytes
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Data block 944 bytes
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Total: 5098 bytes
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