40 lines
893 B
C
40 lines
893 B
C
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#include "crypto_sign.h"
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#include "sha512.h"
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#include "ge.h"
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#include "sc.h"
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int crypto_sign_open(
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unsigned char *m,unsigned long long *mlen,
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const unsigned char *sm,unsigned long long smlen,
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const unsigned char *pk
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)
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{
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unsigned char h[64];
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unsigned char checkr[32];
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ge_p3 A;
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ge_p2 R;
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unsigned long long i;
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*mlen = -1;
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if (smlen < 64) return -1;
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if (sm[63] & 224) return -1;
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if (ge_frombytes_negate_vartime(&A,pk) != 0) return -1;
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for (i = 0;i < smlen;++i) m[i] = sm[i];
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for (i = 0;i < 32;++i) m[32 + i] = pk[i];
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sha512(h,m,smlen);
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sc_reduce(h);
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ge_double_scalarmult_vartime(&R,h,&A,sm + 32);
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ge_tobytes(checkr,&R);
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if (crypto_verify_32(checkr,sm) != 0) {
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for (i = 0;i < smlen;++i) m[i] = 0;
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return -1;
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}
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for (i = 0;i < smlen - 64;++i) m[i] = sm[64 + i];
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for (i = smlen - 64;i < smlen;++i) m[i] = 0;
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*mlen = smlen - 64;
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return 0;
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}
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