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Diffstat (limited to 'src/constructs/tss/tss.cpp')
| -rw-r--r-- | src/constructs/tss/tss.cpp | 263 |
1 files changed, 263 insertions, 0 deletions
diff --git a/src/constructs/tss/tss.cpp b/src/constructs/tss/tss.cpp new file mode 100644 index 000000000..0782a27d1 --- /dev/null +++ b/src/constructs/tss/tss.cpp @@ -0,0 +1,263 @@ +/* +* RTSS (threshold secret sharing) +* (C) 2009 Jack Lloyd +* +* Distributed under the terms of the Botan license +*/ + +#include <botan/tss.h> +#include <botan/loadstor.h> +#include <botan/pipe.h> +#include <botan/hex.h> +#include <botan/sha2_32.h> +#include <botan/sha160.h> +#include <memory> + +namespace Botan { + +namespace { + +/** +Table for GF(2^8) arithmetic (exponentials) +*/ +const byte EXP[256] = { +0x01, 0x03, 0x05, 0x0F, 0x11, 0x33, 0x55, 0xFF, 0x1A, 0x2E, 0x72, +0x96, 0xA1, 0xF8, 0x13, 0x35, 0x5F, 0xE1, 0x38, 0x48, 0xD8, 0x73, +0x95, 0xA4, 0xF7, 0x02, 0x06, 0x0A, 0x1E, 0x22, 0x66, 0xAA, 0xE5, +0x34, 0x5C, 0xE4, 0x37, 0x59, 0xEB, 0x26, 0x6A, 0xBE, 0xD9, 0x70, +0x90, 0xAB, 0xE6, 0x31, 0x53, 0xF5, 0x04, 0x0C, 0x14, 0x3C, 0x44, +0xCC, 0x4F, 0xD1, 0x68, 0xB8, 0xD3, 0x6E, 0xB2, 0xCD, 0x4C, 0xD4, +0x67, 0xA9, 0xE0, 0x3B, 0x4D, 0xD7, 0x62, 0xA6, 0xF1, 0x08, 0x18, +0x28, 0x78, 0x88, 0x83, 0x9E, 0xB9, 0xD0, 0x6B, 0xBD, 0xDC, 0x7F, +0x81, 0x98, 0xB3, 0xCE, 0x49, 0xDB, 0x76, 0x9A, 0xB5, 0xC4, 0x57, +0xF9, 0x10, 0x30, 0x50, 0xF0, 0x0B, 0x1D, 0x27, 0x69, 0xBB, 0xD6, +0x61, 0xA3, 0xFE, 0x19, 0x2B, 0x7D, 0x87, 0x92, 0xAD, 0xEC, 0x2F, +0x71, 0x93, 0xAE, 0xE9, 0x20, 0x60, 0xA0, 0xFB, 0x16, 0x3A, 0x4E, +0xD2, 0x6D, 0xB7, 0xC2, 0x5D, 0xE7, 0x32, 0x56, 0xFA, 0x15, 0x3F, +0x41, 0xC3, 0x5E, 0xE2, 0x3D, 0x47, 0xC9, 0x40, 0xC0, 0x5B, 0xED, +0x2C, 0x74, 0x9C, 0xBF, 0xDA, 0x75, 0x9F, 0xBA, 0xD5, 0x64, 0xAC, +0xEF, 0x2A, 0x7E, 0x82, 0x9D, 0xBC, 0xDF, 0x7A, 0x8E, 0x89, 0x80, +0x9B, 0xB6, 0xC1, 0x58, 0xE8, 0x23, 0x65, 0xAF, 0xEA, 0x25, 0x6F, +0xB1, 0xC8, 0x43, 0xC5, 0x54, 0xFC, 0x1F, 0x21, 0x63, 0xA5, 0xF4, +0x07, 0x09, 0x1B, 0x2D, 0x77, 0x99, 0xB0, 0xCB, 0x46, 0xCA, 0x45, +0xCF, 0x4A, 0xDE, 0x79, 0x8B, 0x86, 0x91, 0xA8, 0xE3, 0x3E, 0x42, +0xC6, 0x51, 0xF3, 0x0E, 0x12, 0x36, 0x5A, 0xEE, 0x29, 0x7B, 0x8D, +0x8C, 0x8F, 0x8A, 0x85, 0x94, 0xA7, 0xF2, 0x0D, 0x17, 0x39, 0x4B, +0xDD, 0x7C, 0x84, 0x97, 0xA2, 0xFD, 0x1C, 0x24, 0x6C, 0xB4, 0xC7, +0x52, 0xF6, 0x01 }; + +/** +Table for GF(2^8) arithmetic (logarithms) +*/ +const byte LOG[] = { +0x90, 0x00, 0x19, 0x01, 0x32, 0x02, 0x1A, 0xC6, 0x4B, 0xC7, 0x1B, +0x68, 0x33, 0xEE, 0xDF, 0x03, 0x64, 0x04, 0xE0, 0x0E, 0x34, 0x8D, +0x81, 0xEF, 0x4C, 0x71, 0x08, 0xC8, 0xF8, 0x69, 0x1C, 0xC1, 0x7D, +0xC2, 0x1D, 0xB5, 0xF9, 0xB9, 0x27, 0x6A, 0x4D, 0xE4, 0xA6, 0x72, +0x9A, 0xC9, 0x09, 0x78, 0x65, 0x2F, 0x8A, 0x05, 0x21, 0x0F, 0xE1, +0x24, 0x12, 0xF0, 0x82, 0x45, 0x35, 0x93, 0xDA, 0x8E, 0x96, 0x8F, +0xDB, 0xBD, 0x36, 0xD0, 0xCE, 0x94, 0x13, 0x5C, 0xD2, 0xF1, 0x40, +0x46, 0x83, 0x38, 0x66, 0xDD, 0xFD, 0x30, 0xBF, 0x06, 0x8B, 0x62, +0xB3, 0x25, 0xE2, 0x98, 0x22, 0x88, 0x91, 0x10, 0x7E, 0x6E, 0x48, +0xC3, 0xA3, 0xB6, 0x1E, 0x42, 0x3A, 0x6B, 0x28, 0x54, 0xFA, 0x85, +0x3D, 0xBA, 0x2B, 0x79, 0x0A, 0x15, 0x9B, 0x9F, 0x5E, 0xCA, 0x4E, +0xD4, 0xAC, 0xE5, 0xF3, 0x73, 0xA7, 0x57, 0xAF, 0x58, 0xA8, 0x50, +0xF4, 0xEA, 0xD6, 0x74, 0x4F, 0xAE, 0xE9, 0xD5, 0xE7, 0xE6, 0xAD, +0xE8, 0x2C, 0xD7, 0x75, 0x7A, 0xEB, 0x16, 0x0B, 0xF5, 0x59, 0xCB, +0x5F, 0xB0, 0x9C, 0xA9, 0x51, 0xA0, 0x7F, 0x0C, 0xF6, 0x6F, 0x17, +0xC4, 0x49, 0xEC, 0xD8, 0x43, 0x1F, 0x2D, 0xA4, 0x76, 0x7B, 0xB7, +0xCC, 0xBB, 0x3E, 0x5A, 0xFB, 0x60, 0xB1, 0x86, 0x3B, 0x52, 0xA1, +0x6C, 0xAA, 0x55, 0x29, 0x9D, 0x97, 0xB2, 0x87, 0x90, 0x61, 0xBE, +0xDC, 0xFC, 0xBC, 0x95, 0xCF, 0xCD, 0x37, 0x3F, 0x5B, 0xD1, 0x53, +0x39, 0x84, 0x3C, 0x41, 0xA2, 0x6D, 0x47, 0x14, 0x2A, 0x9E, 0x5D, +0x56, 0xF2, 0xD3, 0xAB, 0x44, 0x11, 0x92, 0xD9, 0x23, 0x20, 0x2E, +0x89, 0xB4, 0x7C, 0xB8, 0x26, 0x77, 0x99, 0xE3, 0xA5, 0x67, 0x4A, +0xED, 0xDE, 0xC5, 0x31, 0xFE, 0x18, 0x0D, 0x63, 0x8C, 0x80, 0xC0, +0xF7, 0x70, 0x07 }; + +byte gfp_mul(byte x, byte y) + { + if(x == 0 || y == 0) + return 0; + return EXP[(LOG[x] + LOG[y]) % 255]; + } + +byte rtss_hash_id(const std::string& hash_name) + { + if(hash_name == "SHA-160") + return 1; + else if(hash_name == "SHA-256") + return 2; + else + throw Invalid_Argument("RTSS only supports SHA-1 and SHA-256"); + } + +HashFunction* get_rtss_hash_by_id(byte id) + { + if(id == 1) + return new SHA_160; + else if(id == 2) + return new SHA_256; + else + throw Decoding_Error("Bad RTSS hash identifier"); + } + +} + +RTSS_Share::RTSS_Share(const std::string& hex_input) + { + Pipe pipe(new Hex_Decoder); + pipe.process_msg(hex_input); + contents = pipe.read_all(); + } + +byte RTSS_Share::share_id() const + { + if(!initialized()) + throw Invalid_State("RTSS_Share::share_id not initialized"); + + return contents[20]; + } + +std::string RTSS_Share::to_string() const + { + Pipe pipe(new Hex_Encoder); + pipe.process_msg(contents); + return pipe.read_all_as_string(); + } + +std::vector<RTSS_Share> +RTSS_Share::split(byte M, byte N, + const byte S[], u16bit S_len, + const byte identifier[16], + RandomNumberGenerator& rng) + { + if(M == 0 || N == 0 || M > N) + throw Encoding_Error("RTSS_Share::split: M == 0 or N == 0 or M > N"); + + SHA_256 hash; // always use SHA-256 when generating shares + + std::vector<RTSS_Share> shares(N); + + // Create RTSS header in each share + for(byte i = 0; i != N; ++i) + { + shares[i].contents.append(identifier, 16); + shares[i].contents.append(rtss_hash_id(hash.name())); + shares[i].contents.append(M); + shares[i].contents.append(get_byte(0, S_len)); + shares[i].contents.append(get_byte(1, S_len)); + } + + // Choose sequential values for X starting from 1 + for(byte i = 0; i != N; ++i) + shares[i].contents.append(i+1); + + // secret = S || H(S) + SecureVector<byte> secret(S, S_len); + secret.append(hash.process(S, S_len)); + + for(size_t i = 0; i != secret.size(); ++i) + { + std::vector<byte> coefficients(M-1); + rng.randomize(&coefficients[0], coefficients.size()); + + for(byte j = 0; j != N; ++j) + { + const byte X = j + 1; + + byte sum = secret[i]; + byte X_i = X; + + for(size_t k = 0; k != coefficients.size(); ++k) + { + sum ^= gfp_mul(X_i, coefficients[k]); + X_i = gfp_mul(X_i, X); + } + + shares[j].contents.append(sum); + } + } + + return shares; + } + +SecureVector<byte> +RTSS_Share::reconstruct(const std::vector<RTSS_Share>& shares) + { + const u32bit RTSS_HEADER_SIZE = 20; + + for(size_t i = 0; i != shares.size(); ++i) + { + if(shares[i].size() != shares[0].size()) + throw Decoding_Error("Different sized RTSS shares detected"); + if(shares[i].share_id() == 0) + throw Decoding_Error("Invalid (id = 0) RTSS share detected"); + if(shares[i].size() < RTSS_HEADER_SIZE) + throw Decoding_Error("Missing or malformed RTSS header"); + + if(!same_mem(shares[0].contents.begin(), + shares[i].contents.begin(), RTSS_HEADER_SIZE)) + throw Decoding_Error("Different RTSS headers detected"); + } + + if(shares.size() < shares[0].contents[17]) + throw Decoding_Error("Insufficient shares to do TSS reconstruction"); + + u16bit secret_len = make_u16bit(shares[0].contents[18], + shares[0].contents[19]); + + byte hash_id = shares[0].contents[16]; + + std::auto_ptr<HashFunction> hash(get_rtss_hash_by_id(hash_id)); + + if(shares[0].size() != secret_len + hash->OUTPUT_LENGTH + RTSS_HEADER_SIZE + 1) + throw Decoding_Error("Bad RTSS length field in header"); + + std::vector<byte> V(shares.size()); + SecureVector<byte> secret; + + for(size_t i = RTSS_HEADER_SIZE + 1; i != shares[0].size(); ++i) + { + for(size_t j = 0; j != V.size(); ++j) + V[j] = shares[j].contents[i]; + + byte r = 0; + for(size_t k = 0; k != shares.size(); ++k) + { + // L_i function: + byte r2 = 1; + for(size_t l = 0; l != shares.size(); ++l) + { + if(k == l) + continue; + + byte share_k = shares[k].share_id(); + byte share_l = shares[l].share_id(); + + if(share_k == share_l) + throw Decoding_Error("Duplicate shares found in RTSS recovery"); + + byte div = EXP[(255 + LOG[share_l] - LOG[share_k ^ share_l]) % 255]; + + r2 = gfp_mul(r2, div); + } + + r ^= gfp_mul(V[k], r2); + } + secret.append(r); + } + + if(secret.size() != secret_len + hash->OUTPUT_LENGTH) + throw Decoding_Error("Bad length in RTSS output"); + + hash->update(secret, secret_len); + SecureVector<byte> hash_check = hash->final(); + + if(!same_mem(hash_check.begin(), secret + secret_len, hash->OUTPUT_LENGTH)) + throw Decoding_Error("RTSS hash check failed"); + + return SecureVector<byte>(secret, secret_len); + } + +} |