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#include <string.h>
#include "crypto_sign.h"
#include "crypto_hash_sha512.h"
#include "crypto_verify_32.h"
#include "ge.h"
#include "sc.h"
int crypto_sign_open(
unsigned char *m,unsigned long long *mlen,
const unsigned char *sm,unsigned long long smlen,
const unsigned char *pk
)
{
unsigned char pkcopy[32];
unsigned char rcopy[32];
unsigned char scopy[32];
unsigned char h[64];
unsigned char rcheck[32];
ge_p3 A;
ge_p2 R;
if (smlen < 64) goto badsig;
if (sm[63] & 224) goto badsig;
if (ge_frombytes_negate_vartime(&A,pk) != 0) goto badsig;
memmove(pkcopy,pk,32);
memmove(rcopy,sm,32);
memmove(scopy,sm + 32,32);
memmove(m,sm,smlen);
memmove(m + 32,pkcopy,32);
crypto_hash_sha512(h,m,smlen);
sc_reduce(h);
ge_double_scalarmult_vartime(&R,h,&A,scopy);
ge_tobytes(rcheck,&R);
if (crypto_verify_32(rcheck,rcopy) == 0) {
memmove(m,m + 64,smlen - 64);
memset(m + smlen - 64,0,64);
*mlen = smlen - 64;
return 0;
}
badsig:
*mlen = -1;
memset(m,0,smlen);
return -1;
}
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