282 lines
16 KiB
Rust
282 lines
16 KiB
Rust
//! CSS specification tables — mathematical constants defining the cipher.
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//!
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//! These 5 tables are the fixed permutations and substitutions of the
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//! Content Scramble System. They are mathematical constants derived from
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//! the CSS specification, published in academic literature since 1999.
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/// Table 1: byte substitution used in key mangling and sector seed processing.
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pub const TAB1: [u8; 256] = [
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0x33, 0x73, 0x3b, 0x26, 0x63, 0x23, 0x6b, 0x76, 0x3e, 0x7e, 0x36, 0x2b, 0x6e, 0x2e, 0x66, 0x7b,
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0xd3, 0x93, 0xdb, 0x06, 0x43, 0x03, 0x4b, 0x96, 0xde, 0x9e, 0xd6, 0x0b, 0x4e, 0x0e, 0x46, 0x9b,
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0x57, 0x17, 0x5f, 0x82, 0xc7, 0x87, 0xcf, 0x12, 0x5a, 0x1a, 0x52, 0x8f, 0xca, 0x8a, 0xc2, 0x1f,
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0xd9, 0x99, 0xd1, 0x00, 0x49, 0x09, 0x41, 0x90, 0xd8, 0x98, 0xd0, 0x01, 0x48, 0x08, 0x40, 0x91,
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0x3d, 0x7d, 0x35, 0x24, 0x6d, 0x2d, 0x65, 0x74, 0x3c, 0x7c, 0x34, 0x25, 0x6c, 0x2c, 0x64, 0x75,
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0xdd, 0x9d, 0xd5, 0x04, 0x4d, 0x0d, 0x45, 0x94, 0xdc, 0x9c, 0xd4, 0x05, 0x4c, 0x0c, 0x44, 0x95,
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0x59, 0x19, 0x51, 0x80, 0xc9, 0x89, 0xc1, 0x10, 0x58, 0x18, 0x50, 0x81, 0xc8, 0x88, 0xc0, 0x11,
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0xd7, 0x97, 0xdf, 0x02, 0x47, 0x07, 0x4f, 0x92, 0xda, 0x9a, 0xd2, 0x0f, 0x4a, 0x0a, 0x42, 0x9f,
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0x53, 0x13, 0x5b, 0x86, 0xc3, 0x83, 0xcb, 0x16, 0x5e, 0x1e, 0x56, 0x8b, 0xce, 0x8e, 0xc6, 0x1b,
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0xb3, 0xf3, 0xbb, 0xa6, 0xe3, 0xa3, 0xeb, 0xf6, 0xbe, 0xfe, 0xb6, 0xab, 0xee, 0xae, 0xe6, 0xfb,
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0x37, 0x77, 0x3f, 0x22, 0x67, 0x27, 0x6f, 0x72, 0x3a, 0x7a, 0x32, 0x2f, 0x6a, 0x2a, 0x62, 0x7f,
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0xb9, 0xf9, 0xb1, 0xa0, 0xe9, 0xa9, 0xe1, 0xf0, 0xb8, 0xf8, 0xb0, 0xa1, 0xe8, 0xa8, 0xe0, 0xf1,
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0x5d, 0x1d, 0x55, 0x84, 0xcd, 0x8d, 0xc5, 0x14, 0x5c, 0x1c, 0x54, 0x85, 0xcc, 0x8c, 0xc4, 0x15,
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0xbd, 0xfd, 0xb5, 0xa4, 0xed, 0xad, 0xe5, 0xf4, 0xbc, 0xfc, 0xb4, 0xa5, 0xec, 0xac, 0xe4, 0xf5,
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0x39, 0x79, 0x31, 0x20, 0x69, 0x29, 0x61, 0x70, 0x38, 0x78, 0x30, 0x21, 0x68, 0x28, 0x60, 0x71,
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0xb7, 0xf7, 0xbf, 0xa2, 0xe7, 0xa7, 0xef, 0xf2, 0xba, 0xfa, 0xb2, 0xaf, 0xea, 0xaa, 0xe2, 0xff,
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];
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/// Table 2: LFSR1 high-byte feedback permutation.
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pub const TAB2: [u8; 256] = [
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0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x09, 0x08, 0x0b, 0x0a, 0x0d, 0x0c, 0x0f, 0x0e,
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0x12, 0x13, 0x10, 0x11, 0x16, 0x17, 0x14, 0x15, 0x1b, 0x1a, 0x19, 0x18, 0x1f, 0x1e, 0x1d, 0x1c,
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0x24, 0x25, 0x26, 0x27, 0x20, 0x21, 0x22, 0x23, 0x2d, 0x2c, 0x2f, 0x2e, 0x29, 0x28, 0x2b, 0x2a,
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0x36, 0x37, 0x34, 0x35, 0x32, 0x33, 0x30, 0x31, 0x3f, 0x3e, 0x3d, 0x3c, 0x3b, 0x3a, 0x39, 0x38,
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0x49, 0x48, 0x4b, 0x4a, 0x4d, 0x4c, 0x4f, 0x4e, 0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47,
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0x5b, 0x5a, 0x59, 0x58, 0x5f, 0x5e, 0x5d, 0x5c, 0x52, 0x53, 0x50, 0x51, 0x56, 0x57, 0x54, 0x55,
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0x6d, 0x6c, 0x6f, 0x6e, 0x69, 0x68, 0x6b, 0x6a, 0x64, 0x65, 0x66, 0x67, 0x60, 0x61, 0x62, 0x63,
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0x7f, 0x7e, 0x7d, 0x7c, 0x7b, 0x7a, 0x79, 0x78, 0x76, 0x77, 0x74, 0x75, 0x72, 0x73, 0x70, 0x71,
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0x92, 0x93, 0x90, 0x91, 0x96, 0x97, 0x94, 0x95, 0x9b, 0x9a, 0x99, 0x98, 0x9f, 0x9e, 0x9d, 0x9c,
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0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x89, 0x88, 0x8b, 0x8a, 0x8d, 0x8c, 0x8f, 0x8e,
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0xb6, 0xb7, 0xb4, 0xb5, 0xb2, 0xb3, 0xb0, 0xb1, 0xbf, 0xbe, 0xbd, 0xbc, 0xbb, 0xba, 0xb9, 0xb8,
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0xa4, 0xa5, 0xa6, 0xa7, 0xa0, 0xa1, 0xa2, 0xa3, 0xad, 0xac, 0xaf, 0xae, 0xa9, 0xa8, 0xab, 0xaa,
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0xdb, 0xda, 0xd9, 0xd8, 0xdf, 0xde, 0xdd, 0xdc, 0xd2, 0xd3, 0xd0, 0xd1, 0xd6, 0xd7, 0xd4, 0xd5,
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0xc9, 0xc8, 0xcb, 0xca, 0xcd, 0xcc, 0xcf, 0xce, 0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7,
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0xed, 0xec, 0xef, 0xee, 0xe9, 0xe8, 0xeb, 0xea, 0xe4, 0xe5, 0xe6, 0xe7, 0xe0, 0xe1, 0xe2, 0xe3,
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0xff, 0xfe, 0xfd, 0xfc, 0xfb, 0xfa, 0xf9, 0xf8, 0xf6, 0xf7, 0xf4, 0xf5, 0xf2, 0xf3, 0xf0, 0xf1,
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];
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/// Table 3: LFSR1 9-bit low-word feedback table (512 entries).
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///
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/// Indexed by the 9-bit LFSR1 low word (the upper feedback bit makes the
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/// index 9-bit, hence 512 entries, not 256).
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pub const TAB3: [u8; 512] = [
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0x00, 0x24, 0x49, 0x6d, 0x92, 0xb6, 0xdb, 0xff, 0x00, 0x24, 0x49, 0x6d, 0x92, 0xb6, 0xdb, 0xff,
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0x00, 0x24, 0x49, 0x6d, 0x92, 0xb6, 0xdb, 0xff, 0x00, 0x24, 0x49, 0x6d, 0x92, 0xb6, 0xdb, 0xff,
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0x00, 0x24, 0x49, 0x6d, 0x92, 0xb6, 0xdb, 0xff, 0x00, 0x24, 0x49, 0x6d, 0x92, 0xb6, 0xdb, 0xff,
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0x00, 0x24, 0x49, 0x6d, 0x92, 0xb6, 0xdb, 0xff, 0x00, 0x24, 0x49, 0x6d, 0x92, 0xb6, 0xdb, 0xff,
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0x00, 0x24, 0x49, 0x6d, 0x92, 0xb6, 0xdb, 0xff, 0x00, 0x24, 0x49, 0x6d, 0x92, 0xb6, 0xdb, 0xff,
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0x00, 0x24, 0x49, 0x6d, 0x92, 0xb6, 0xdb, 0xff, 0x00, 0x24, 0x49, 0x6d, 0x92, 0xb6, 0xdb, 0xff,
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0x00, 0x24, 0x49, 0x6d, 0x92, 0xb6, 0xdb, 0xff, 0x00, 0x24, 0x49, 0x6d, 0x92, 0xb6, 0xdb, 0xff,
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0x00, 0x24, 0x49, 0x6d, 0x92, 0xb6, 0xdb, 0xff, 0x00, 0x24, 0x49, 0x6d, 0x92, 0xb6, 0xdb, 0xff,
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0x01, 0x25, 0x48, 0x6c, 0x93, 0xb7, 0xda, 0xfe, 0x01, 0x25, 0x48, 0x6c, 0x93, 0xb7, 0xda, 0xfe,
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0x01, 0x25, 0x48, 0x6c, 0x93, 0xb7, 0xda, 0xfe, 0x01, 0x25, 0x48, 0x6c, 0x93, 0xb7, 0xda, 0xfe,
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0x01, 0x25, 0x48, 0x6c, 0x93, 0xb7, 0xda, 0xfe, 0x01, 0x25, 0x48, 0x6c, 0x93, 0xb7, 0xda, 0xfe,
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0x01, 0x25, 0x48, 0x6c, 0x93, 0xb7, 0xda, 0xfe, 0x01, 0x25, 0x48, 0x6c, 0x93, 0xb7, 0xda, 0xfe,
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0x01, 0x25, 0x48, 0x6c, 0x93, 0xb7, 0xda, 0xfe, 0x01, 0x25, 0x48, 0x6c, 0x93, 0xb7, 0xda, 0xfe,
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0x01, 0x25, 0x48, 0x6c, 0x93, 0xb7, 0xda, 0xfe, 0x01, 0x25, 0x48, 0x6c, 0x93, 0xb7, 0xda, 0xfe,
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0x01, 0x25, 0x48, 0x6c, 0x93, 0xb7, 0xda, 0xfe, 0x01, 0x25, 0x48, 0x6c, 0x93, 0xb7, 0xda, 0xfe,
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0x01, 0x25, 0x48, 0x6c, 0x93, 0xb7, 0xda, 0xfe, 0x01, 0x25, 0x48, 0x6c, 0x93, 0xb7, 0xda, 0xfe,
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0x02, 0x26, 0x4b, 0x6f, 0x90, 0xb4, 0xd9, 0xfd, 0x02, 0x26, 0x4b, 0x6f, 0x90, 0xb4, 0xd9, 0xfd,
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0x02, 0x26, 0x4b, 0x6f, 0x90, 0xb4, 0xd9, 0xfd, 0x02, 0x26, 0x4b, 0x6f, 0x90, 0xb4, 0xd9, 0xfd,
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0x02, 0x26, 0x4b, 0x6f, 0x90, 0xb4, 0xd9, 0xfd, 0x02, 0x26, 0x4b, 0x6f, 0x90, 0xb4, 0xd9, 0xfd,
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0x02, 0x26, 0x4b, 0x6f, 0x90, 0xb4, 0xd9, 0xfd, 0x02, 0x26, 0x4b, 0x6f, 0x90, 0xb4, 0xd9, 0xfd,
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0x02, 0x26, 0x4b, 0x6f, 0x90, 0xb4, 0xd9, 0xfd, 0x02, 0x26, 0x4b, 0x6f, 0x90, 0xb4, 0xd9, 0xfd,
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0x02, 0x26, 0x4b, 0x6f, 0x90, 0xb4, 0xd9, 0xfd, 0x02, 0x26, 0x4b, 0x6f, 0x90, 0xb4, 0xd9, 0xfd,
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0x02, 0x26, 0x4b, 0x6f, 0x90, 0xb4, 0xd9, 0xfd, 0x02, 0x26, 0x4b, 0x6f, 0x90, 0xb4, 0xd9, 0xfd,
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0x02, 0x26, 0x4b, 0x6f, 0x90, 0xb4, 0xd9, 0xfd, 0x02, 0x26, 0x4b, 0x6f, 0x90, 0xb4, 0xd9, 0xfd,
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0x03, 0x27, 0x4a, 0x6e, 0x91, 0xb5, 0xd8, 0xfc, 0x03, 0x27, 0x4a, 0x6e, 0x91, 0xb5, 0xd8, 0xfc,
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0x03, 0x27, 0x4a, 0x6e, 0x91, 0xb5, 0xd8, 0xfc, 0x03, 0x27, 0x4a, 0x6e, 0x91, 0xb5, 0xd8, 0xfc,
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0x03, 0x27, 0x4a, 0x6e, 0x91, 0xb5, 0xd8, 0xfc, 0x03, 0x27, 0x4a, 0x6e, 0x91, 0xb5, 0xd8, 0xfc,
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0x03, 0x27, 0x4a, 0x6e, 0x91, 0xb5, 0xd8, 0xfc, 0x03, 0x27, 0x4a, 0x6e, 0x91, 0xb5, 0xd8, 0xfc,
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0x03, 0x27, 0x4a, 0x6e, 0x91, 0xb5, 0xd8, 0xfc, 0x03, 0x27, 0x4a, 0x6e, 0x91, 0xb5, 0xd8, 0xfc,
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0x03, 0x27, 0x4a, 0x6e, 0x91, 0xb5, 0xd8, 0xfc, 0x03, 0x27, 0x4a, 0x6e, 0x91, 0xb5, 0xd8, 0xfc,
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0x03, 0x27, 0x4a, 0x6e, 0x91, 0xb5, 0xd8, 0xfc, 0x03, 0x27, 0x4a, 0x6e, 0x91, 0xb5, 0xd8, 0xfc,
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0x03, 0x27, 0x4a, 0x6e, 0x91, 0xb5, 0xd8, 0xfc, 0x03, 0x27, 0x4a, 0x6e, 0x91, 0xb5, 0xd8, 0xfc,
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];
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/// Table 4: LFSR0 byte permutation (used in initialization and output).
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pub const TAB4: [u8; 256] = [
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0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0, 0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,
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0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8, 0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8,
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0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4, 0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4,
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0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec, 0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc,
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0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2, 0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2,
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0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea, 0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa,
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0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6, 0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6,
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0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee, 0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe,
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0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1, 0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1,
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0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9, 0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9,
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0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5, 0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5,
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0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed, 0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,
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0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3, 0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3,
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0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb, 0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb,
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0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7, 0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7,
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0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef, 0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff,
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];
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/// Table 5: LFSR1 output permutation used in the keystream combiner.
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/// `TAB5[i] == TAB4[i] ^ 0xFF` (bitwise complement of the TAB4 bit-reversal
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/// table). Applied on the normal descramble/recrypt path (lfsr.rs) as well as
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/// in the key-recovery fallback (crack.rs).
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pub const TAB5: [u8; 256] = [
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0xff, 0x7f, 0xbf, 0x3f, 0xdf, 0x5f, 0x9f, 0x1f, 0xef, 0x6f, 0xaf, 0x2f, 0xcf, 0x4f, 0x8f, 0x0f,
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0xf7, 0x77, 0xb7, 0x37, 0xd7, 0x57, 0x97, 0x17, 0xe7, 0x67, 0xa7, 0x27, 0xc7, 0x47, 0x87, 0x07,
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0xfb, 0x7b, 0xbb, 0x3b, 0xdb, 0x5b, 0x9b, 0x1b, 0xeb, 0x6b, 0xab, 0x2b, 0xcb, 0x4b, 0x8b, 0x0b,
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0xf3, 0x73, 0xb3, 0x33, 0xd3, 0x53, 0x93, 0x13, 0xe3, 0x63, 0xa3, 0x23, 0xc3, 0x43, 0x83, 0x03,
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0xfd, 0x7d, 0xbd, 0x3d, 0xdd, 0x5d, 0x9d, 0x1d, 0xed, 0x6d, 0xad, 0x2d, 0xcd, 0x4d, 0x8d, 0x0d,
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0xf5, 0x75, 0xb5, 0x35, 0xd5, 0x55, 0x95, 0x15, 0xe5, 0x65, 0xa5, 0x25, 0xc5, 0x45, 0x85, 0x05,
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0xf9, 0x79, 0xb9, 0x39, 0xd9, 0x59, 0x99, 0x19, 0xe9, 0x69, 0xa9, 0x29, 0xc9, 0x49, 0x89, 0x09,
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0xf1, 0x71, 0xb1, 0x31, 0xd1, 0x51, 0x91, 0x11, 0xe1, 0x61, 0xa1, 0x21, 0xc1, 0x41, 0x81, 0x01,
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0xfe, 0x7e, 0xbe, 0x3e, 0xde, 0x5e, 0x9e, 0x1e, 0xee, 0x6e, 0xae, 0x2e, 0xce, 0x4e, 0x8e, 0x0e,
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0xf6, 0x76, 0xb6, 0x36, 0xd6, 0x56, 0x96, 0x16, 0xe6, 0x66, 0xa6, 0x26, 0xc6, 0x46, 0x86, 0x06,
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0xfa, 0x7a, 0xba, 0x3a, 0xda, 0x5a, 0x9a, 0x1a, 0xea, 0x6a, 0xaa, 0x2a, 0xca, 0x4a, 0x8a, 0x0a,
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0xf2, 0x72, 0xb2, 0x32, 0xd2, 0x52, 0x92, 0x12, 0xe2, 0x62, 0xa2, 0x22, 0xc2, 0x42, 0x82, 0x02,
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0xfc, 0x7c, 0xbc, 0x3c, 0xdc, 0x5c, 0x9c, 0x1c, 0xec, 0x6c, 0xac, 0x2c, 0xcc, 0x4c, 0x8c, 0x0c,
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0xf4, 0x74, 0xb4, 0x34, 0xd4, 0x54, 0x94, 0x14, 0xe4, 0x64, 0xa4, 0x24, 0xc4, 0x44, 0x84, 0x04,
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0xf8, 0x78, 0xb8, 0x38, 0xd8, 0x58, 0x98, 0x18, 0xe8, 0x68, 0xa8, 0x28, 0xc8, 0x48, 0x88, 0x08,
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0xf0, 0x70, 0xb0, 0x30, 0xd0, 0x50, 0x90, 0x10, 0xe0, 0x60, 0xa0, 0x20, 0xc0, 0x40, 0x80, 0x00,
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];
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#[cfg(test)]
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mod tests {
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use super::*;
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/// Pins the documented relationship `TAB5[i] == TAB4[i] ^ 0xFF` so the
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/// table doc cannot drift from the data.
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#[test]
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fn tab5_is_complement_of_tab4() {
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for i in 0..256 {
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assert_eq!(
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TAB5[i],
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TAB4[i] ^ 0xFF,
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"TAB5[{i:#04x}] != TAB4[{i:#04x}] ^ 0xFF"
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);
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}
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}
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/// TAB1 is a bijection on 0..256. CSS uses it as an invertible output
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/// permutation in css_DecryptKey's chained-XOR rounds; if two inputs
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/// collided, the key mangling would not be invertible.
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///
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/// Mutation: duplicate any value (e.g. set TAB1[1] = TAB1[0]) -> the
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/// "maps two inputs" assert fires.
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#[test]
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|
fn tab1_is_a_permutation() {
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|
let mut seen = [false; 256];
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|
for (i, &v) in TAB1.iter().enumerate() {
|
|
assert!(
|
|
!seen[v as usize],
|
|
"TAB1 maps two inputs to {v:#04x} (collision at index {i:#04x})"
|
|
);
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|
seen[v as usize] = true;
|
|
}
|
|
}
|
|
|
|
/// TAB1's fixed structural anchors from the CSS spec table:
|
|
/// TAB1[0x00] == 0x33 and the inverse TAB1[0x33] == 0x00. These two
|
|
/// entries are the canonical first-row / inverse-lookup landmarks of the
|
|
/// published CSS TAB1 and pin the table's orientation.
|
|
///
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|
/// Grounding: CSS specification TAB1, row 0 col 0 = 0x33; index 0x33
|
|
/// (row 3 col 3) = 0x00.
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|
/// Mutation: change the first literal `0x33` in TAB1 -> first assert fails.
|
|
#[test]
|
|
fn tab1_known_spec_anchors() {
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|
assert_eq!(TAB1[0x00], 0x33, "TAB1[0] is the published 0x33");
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|
assert_eq!(TAB1[0x33], 0x00, "TAB1[0x33] is the published 0x00");
|
|
}
|
|
|
|
/// TAB2 is a permutation of 0..256 (it is the LFSR1 high-byte feedback
|
|
/// substitution). A non-bijective TAB2 would bias the LFSR1 keystream.
|
|
///
|
|
/// Mutation: set TAB2[8] = 0x00 (collides with TAB2[0]) -> assert fires.
|
|
#[test]
|
|
fn tab2_is_a_permutation() {
|
|
let mut seen = [false; 256];
|
|
for (i, &v) in TAB2.iter().enumerate() {
|
|
assert!(
|
|
!seen[v as usize],
|
|
"TAB2 maps two inputs to {v:#04x} (collision at index {i:#04x})"
|
|
);
|
|
seen[v as usize] = true;
|
|
}
|
|
}
|
|
|
|
/// TAB3 is generated by the CSS LFSR1 low-word rule:
|
|
/// TAB3[i] == BASE[i & 7] ^ (i >> 7)
|
|
/// where BASE = [0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff] is the 8-value
|
|
/// feedback block (BASE[j] is the 9-bit-spread of the 3 high feedback
|
|
/// bits). The 9-bit index splits into a 3-bit selector (i & 7) and a
|
|
/// 2-bit carry group (i >> 7) that XORs the base value. This pins all 512
|
|
/// entries to one closed-form spec rule.
|
|
///
|
|
/// Derivation verified offline against the published TAB3 byte layout.
|
|
/// Mutation: flip any single byte in the TAB3 literal (e.g. the 9th entry
|
|
/// 0x00 -> 0x01) -> the formula check fails at that index.
|
|
#[test]
|
|
fn tab3_matches_lfsr1_generating_formula() {
|
|
const BASE: [u8; 8] = [0x00, 0x24, 0x49, 0x6d, 0x92, 0xb6, 0xdb, 0xff];
|
|
for i in 0..512usize {
|
|
let expected = BASE[i & 7] ^ ((i >> 7) as u8);
|
|
assert_eq!(
|
|
TAB3[i], expected,
|
|
"TAB3[{i:#05x}] = {:#04x}, formula BASE[i&7]^(i>>7) = {expected:#04x}",
|
|
TAB3[i]
|
|
);
|
|
}
|
|
}
|
|
|
|
/// TAB4 is the exact bit-reversal of each byte (CSS uses it to permute
|
|
/// LFSR0 bytes on seed and output). TAB4[b] reverses b's 8 bits MSB<->LSB.
|
|
/// Therefore it is also an involution: TAB4[TAB4[b]] == b.
|
|
///
|
|
/// Grounding: TAB4[0x01]=0x80, TAB4[0x80]=0x01, TAB4[0x00]=0x00,
|
|
/// TAB4[0xFF]=0xFF.
|
|
/// Mutation: set TAB4[1] = 0x40 (not the reversal 0x80) -> bit-reversal
|
|
/// check fails at index 1.
|
|
#[test]
|
|
fn tab4_is_exact_bit_reversal_and_involution() {
|
|
for b in 0u16..256 {
|
|
let rev = (0..8).fold(0u8, |acc, k| acc | (((b as u8 >> k) & 1) << (7 - k)));
|
|
assert_eq!(
|
|
TAB4[b as usize], rev,
|
|
"TAB4[{b:#04x}] is not the bit-reversal {rev:#04x}"
|
|
);
|
|
}
|
|
for b in 0..256usize {
|
|
assert_eq!(
|
|
TAB4[TAB4[b] as usize], b as u8,
|
|
"TAB4 not an involution at {b:#04x}"
|
|
);
|
|
}
|
|
// Spec landmark entries.
|
|
assert_eq!(TAB4[0x01], 0x80);
|
|
assert_eq!(TAB4[0x80], 0x01);
|
|
assert_eq!(TAB4[0x00], 0x00);
|
|
assert_eq!(TAB4[0xFF], 0xFF);
|
|
}
|
|
|
|
/// TAB4 is a permutation (bit-reversal is bijective). Distinct from the
|
|
/// reversal test: a table that is "reversal except two swapped entries"
|
|
/// would still be a permutation, and a table that is "reversal except one
|
|
/// duplicated entry" would fail this but might pass a sampled reversal
|
|
/// check — the two tests pin different failure modes.
|
|
///
|
|
/// Mutation: set TAB4[2] = TAB4[1] -> permutation assert fires.
|
|
#[test]
|
|
fn tab4_is_a_permutation() {
|
|
let mut seen = [false; 256];
|
|
for &v in TAB4.iter() {
|
|
assert!(!seen[v as usize], "TAB4 maps two inputs to {v:#04x}");
|
|
seen[v as usize] = true;
|
|
}
|
|
}
|
|
|
|
/// TAB5 is also a permutation (complement of a bijection is a bijection)
|
|
/// and its own self-consistency landmark: TAB5[0x00] == 0xFF (TAB4[0]^0xFF)
|
|
/// and TAB5[0xFF] == 0x00 (TAB4[0xFF]^0xFF). Pins orientation independent
|
|
/// of the complement-loop test.
|
|
///
|
|
/// Mutation: change the first TAB5 literal 0xff -> 0xfe -> the landmark
|
|
/// and permutation checks both catch it.
|
|
#[test]
|
|
fn tab5_is_permutation_with_anchors() {
|
|
let mut seen = [false; 256];
|
|
for &v in TAB5.iter() {
|
|
assert!(!seen[v as usize], "TAB5 maps two inputs to {v:#04x}");
|
|
seen[v as usize] = true;
|
|
}
|
|
assert_eq!(TAB5[0x00], 0xFF, "TAB5[0] = TAB4[0]^0xFF = 0xFF");
|
|
assert_eq!(TAB5[0xFF], 0x00, "TAB5[0xFF] = TAB4[0xFF]^0xFF = 0x00");
|
|
}
|
|
}
|