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secp256k1_fe_sqrt: Verify that the arguments don't alias.

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Russell O'Connor 2018-08-14 16:47:14 -04:00
parent 1e6f1f5ad5
commit bf8b86cc07
1 changed files with 2 additions and 0 deletions
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src/field_impl.h
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@ -48,6 +48,8 @@ static int secp256k1_fe_sqrt(secp256k1_fe *r, const secp256k1_fe *a) {
secp256k1_fe x2, x3, x6, x9, x11, x22, x44, x88, x176, x220, x223, t1; secp256k1_fe x2, x3, x6, x9, x11, x22, x44, x88, x176, x220, x223, t1;
int j; int j;
VERIFY_CHECK(r != a);
/** The binary representation of (p + 1)/4 has 3 blocks of 1s, with lengths in /** The binary representation of (p + 1)/4 has 3 blocks of 1s, with lengths in
* { 2, 22, 223 }. Use an addition chain to calculate 2^n - 1 for each block: * { 2, 22, 223 }. Use an addition chain to calculate 2^n - 1 for each block:
* 1, [2], 3, 6, 9, 11, [22], 44, 88, 176, 220, [223] * 1, [2], 3, 6, 9, 11, [22], 44, 88, 176, 220, [223]