35 lines
795 B
C
35 lines
795 B
C
#include "fe25519.h"
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// tmp MUST != out or in
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// in MAY == out
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void fe25519_batchinvert(fe25519 *out, const fe25519 *in, fe25519 *tmp, size_t num, size_t offset)
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{
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fe25519 acc;
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fe25519 tmpacc;
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size_t i;
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const fe25519 *inp;
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fe25519 *outp;
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fe25519_setint(&acc,1);
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inp = in;
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for (i = 0;i < num;++i) {
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tmp[i] = acc;
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fe25519_mul(&acc,&acc,inp);
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inp = (const fe25519 *)((const char *)inp + offset);
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}
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fe25519_invert(&acc,&acc);
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i = num;
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inp = (const fe25519 *)((const char *)in + offset * num);
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outp = (fe25519 *)((char *)out + offset * num);
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while (i--) {
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inp = (const fe25519 *)((const char *)inp - offset);
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outp = (fe25519 *)((char *)outp - offset);
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fe25519_mul(&tmpacc,&acc,inp);
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fe25519_mul(outp,&acc,&tmp[i]);
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acc = tmpacc;
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}
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}
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