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I2P: End-to-End encrypted and anonymous Internet
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102 lines
2.6 KiB
102 lines
2.6 KiB
#include "Crypto.h" |
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#include "Elligator.h" |
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namespace i2p |
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{ |
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namespace crypto |
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{ |
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static const uint8_t u_[32] = |
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{ |
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0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, |
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 |
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}; |
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Elligator2::Elligator2 () |
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{ |
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// TODO: share with Ed22519 |
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p = BN_new (); |
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// 2^255-19 |
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BN_set_bit (p, 255); // 2^255 |
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BN_sub_word (p, 19); |
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p38 = BN_dup (p); BN_add_word (p38, 3); BN_div_word (p38, 8); // (p+3)/8 |
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p12 = BN_dup (p); BN_sub_word (p12, 1); BN_div_word (p12, 2); // (p-1)/2 |
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n1 = BN_dup (p); BN_sub_word (n1, 1); // p-1 |
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n2 = BN_dup (p); BN_sub_word (n2, 2); // p-2 |
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A = BN_new (); BN_set_word (A, 486662); |
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nA = BN_new (); BN_sub (nA, p, A); |
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BN_CTX * ctx = BN_CTX_new (); |
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// calculate sqrt(-1) |
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sqrtn1 = BN_new (); |
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BN_mod_exp (sqrtn1, n1, p38, p, ctx); // (-1)^((p+3)/8) |
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auto p14 = BN_dup (p); BN_sub_word (p14, 1); BN_div_word (p14, 4); // (p-1)/4 |
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auto tmp = BN_new (); BN_set_word (tmp, 2); |
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BN_mod_exp (tmp, tmp, p14, p, ctx); // 2^((p-1)/4 |
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BN_mod_mul (sqrtn1, tmp, sqrtn1, p, ctx); // 2^((p-1)/4 * (-1)^((p+3)/8) |
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BN_free (p14); |
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u = BN_new (); BN_bin2bn (u_, 32, u); // TODO: endianess |
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iu = BN_new (); BN_mod_inverse (iu, u, p, ctx); |
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// calculate d = -121665*inv(121666) |
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d = BN_new (); |
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BN_set_word (tmp, 121666); |
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BN_mod_inverse (tmp, tmp, p, ctx); |
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BN_set_word (d, 121665); |
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BN_set_negative (d, 1); |
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BN_mod_mul (d, d, tmp, p, ctx); |
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BN_free (tmp); |
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//printf ("%s\n", BN_bn2hex (d)); |
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BN_CTX_free (ctx); |
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} |
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Elligator2::~Elligator2 () |
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{ |
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BN_free (p); BN_free (p38); BN_free (p12); |
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BN_free (n1);BN_free (n2); BN_free (sqrtn1); |
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BN_free (A); BN_free (nA); |
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BN_free (u); BN_free (iu); BN_free (d); |
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} |
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void Elligator2::Encode (const uint8_t * key, uint8_t * encoded) const |
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{ |
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BN_CTX * ctx = BN_CTX_new (); |
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BN_CTX_start (ctx); |
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BIGNUM * a = BN_CTX_get (ctx); BN_bin2bn (key, 32, a); |
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BIGNUM * b = BN_CTX_get (ctx); |
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BN_add (a, A, b); |
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BIGNUM * c = BN_CTX_get (ctx); |
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BN_mod_exp (c, b, n2, p, ctx); |
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BN_mod_mul (b, c, a, p, ctx); |
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BN_sub (b, p, b); |
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//BN_mod_exp (c, b, n2, p, ctx); |
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BN_mod_mul (c, b, iu, p, ctx); |
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// TODO: |
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bn2buf (b, encoded, 32); |
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BN_CTX_end (ctx); |
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BN_CTX_free (ctx); |
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} |
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static std::unique_ptr<Elligator2> g_Elligator; |
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std::unique_ptr<Elligator2>& GetElligator () |
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{ |
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if (!g_Elligator) |
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{ |
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auto el = new Elligator2(); |
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if (!g_Elligator) // make sure it was not created already |
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g_Elligator.reset (el); |
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else |
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delete el; |
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} |
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return g_Elligator; |
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} |
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} |
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} |
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