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author | Riccardo Spagni <ric@spagni.net> | 2015-08-24 19:34:10 +0200 |
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committer | Riccardo Spagni <ric@spagni.net> | 2015-10-26 18:00:53 +0200 |
commit | bb0c161e7d4bff0e70b59c2f4267da96f34742af (patch) | |
tree | 6218bba2ad3cdaa4a8c0be027587db736a2cc946 /src/crypto/shen_ed25519_ref/ref10CommentedCombined/fe_tobytes.c | |
parent | Merge pull request #448 (diff) | |
download | monero-bb0c161e7d4bff0e70b59c2f4267da96f34742af.tar.xz |
renamed folder
Diffstat (limited to 'src/crypto/shen_ed25519_ref/ref10CommentedCombined/fe_tobytes.c')
-rw-r--r-- | src/crypto/shen_ed25519_ref/ref10CommentedCombined/fe_tobytes.c | 119 |
1 files changed, 0 insertions, 119 deletions
diff --git a/src/crypto/shen_ed25519_ref/ref10CommentedCombined/fe_tobytes.c b/src/crypto/shen_ed25519_ref/ref10CommentedCombined/fe_tobytes.c deleted file mode 100644 index 0a63baf9c..000000000 --- a/src/crypto/shen_ed25519_ref/ref10CommentedCombined/fe_tobytes.c +++ /dev/null @@ -1,119 +0,0 @@ -#include "fe.h" - -/* -Preconditions: - |h| bounded by 1.1*2^26,1.1*2^25,1.1*2^26,1.1*2^25,etc. - -Write p=2^255-19; q=floor(h/p). -Basic claim: q = floor(2^(-255)(h + 19 2^(-25)h9 + 2^(-1))). - -Proof: - Have |h|<=p so |q|<=1 so |19^2 2^(-255) q|<1/4. - Also have |h-2^230 h9|<2^231 so |19 2^(-255)(h-2^230 h9)|<1/4. - - Write y=2^(-1)-19^2 2^(-255)q-19 2^(-255)(h-2^230 h9). - Then 0<y<1. - - Write r=h-pq. - Have 0<=r<=p-1=2^255-20. - Thus 0<=r+19(2^-255)r<r+19(2^-255)2^255<=2^255-1. - - Write x=r+19(2^-255)r+y. - Then 0<x<2^255 so floor(2^(-255)x) = 0 so floor(q+2^(-255)x) = q. - - Have q+2^(-255)x = 2^(-255)(h + 19 2^(-25) h9 + 2^(-1)) - so floor(2^(-255)(h + 19 2^(-25) h9 + 2^(-1))) = q. -*/ - -void fe_tobytes(unsigned char *s,const fe h) -{ - crypto_int32 h0 = h[0]; - crypto_int32 h1 = h[1]; - crypto_int32 h2 = h[2]; - crypto_int32 h3 = h[3]; - crypto_int32 h4 = h[4]; - crypto_int32 h5 = h[5]; - crypto_int32 h6 = h[6]; - crypto_int32 h7 = h[7]; - crypto_int32 h8 = h[8]; - crypto_int32 h9 = h[9]; - crypto_int32 q; - crypto_int32 carry0; - crypto_int32 carry1; - crypto_int32 carry2; - crypto_int32 carry3; - crypto_int32 carry4; - crypto_int32 carry5; - crypto_int32 carry6; - crypto_int32 carry7; - crypto_int32 carry8; - crypto_int32 carry9; - - q = (19 * h9 + (((crypto_int32) 1) << 24)) >> 25; - q = (h0 + q) >> 26; - q = (h1 + q) >> 25; - q = (h2 + q) >> 26; - q = (h3 + q) >> 25; - q = (h4 + q) >> 26; - q = (h5 + q) >> 25; - q = (h6 + q) >> 26; - q = (h7 + q) >> 25; - q = (h8 + q) >> 26; - q = (h9 + q) >> 25; - - /* Goal: Output h-(2^255-19)q, which is between 0 and 2^255-20. */ - h0 += 19 * q; - /* Goal: Output h-2^255 q, which is between 0 and 2^255-20. */ - - carry0 = h0 >> 26; h1 += carry0; h0 -= carry0 << 26; - carry1 = h1 >> 25; h2 += carry1; h1 -= carry1 << 25; - carry2 = h2 >> 26; h3 += carry2; h2 -= carry2 << 26; - carry3 = h3 >> 25; h4 += carry3; h3 -= carry3 << 25; - carry4 = h4 >> 26; h5 += carry4; h4 -= carry4 << 26; - carry5 = h5 >> 25; h6 += carry5; h5 -= carry5 << 25; - carry6 = h6 >> 26; h7 += carry6; h6 -= carry6 << 26; - carry7 = h7 >> 25; h8 += carry7; h7 -= carry7 << 25; - carry8 = h8 >> 26; h9 += carry8; h8 -= carry8 << 26; - carry9 = h9 >> 25; h9 -= carry9 << 25; - /* h10 = carry9 */ - - /* - Goal: Output h0+...+2^255 h10-2^255 q, which is between 0 and 2^255-20. - Have h0+...+2^230 h9 between 0 and 2^255-1; - evidently 2^255 h10-2^255 q = 0. - Goal: Output h0+...+2^230 h9. - */ - - s[0] = h0 >> 0; - s[1] = h0 >> 8; - s[2] = h0 >> 16; - s[3] = (h0 >> 24) | (h1 << 2); - s[4] = h1 >> 6; - s[5] = h1 >> 14; - s[6] = (h1 >> 22) | (h2 << 3); - s[7] = h2 >> 5; - s[8] = h2 >> 13; - s[9] = (h2 >> 21) | (h3 << 5); - s[10] = h3 >> 3; - s[11] = h3 >> 11; - s[12] = (h3 >> 19) | (h4 << 6); - s[13] = h4 >> 2; - s[14] = h4 >> 10; - s[15] = h4 >> 18; - s[16] = h5 >> 0; - s[17] = h5 >> 8; - s[18] = h5 >> 16; - s[19] = (h5 >> 24) | (h6 << 1); - s[20] = h6 >> 7; - s[21] = h6 >> 15; - s[22] = (h6 >> 23) | (h7 << 3); - s[23] = h7 >> 5; - s[24] = h7 >> 13; - s[25] = (h7 >> 21) | (h8 << 4); - s[26] = h8 >> 4; - s[27] = h8 >> 12; - s[28] = (h8 >> 20) | (h9 << 6); - s[29] = h9 >> 2; - s[30] = h9 >> 10; - s[31] = h9 >> 18; -} |