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fix bad computed values

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This commit is contained in:
Ludovic FLAMENT
2015-09-25 23:52:08 +02:00
parent ae6b4be135
commit 71576aef14
1 changed files with 9 additions and 6 deletions
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15
wolfcrypt/src/idea.c
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@@ -48,17 +48,20 @@ static INLINE word16 idea_mult(word16 x, word16 y)
{ {
long mul, res; long mul, res;
mul = x * y; mul = (long)x * (long)y;
if (mul) { if (mul) {
res = (mul & IDEA_MASK) - (mul >> 16); res = (mul & IDEA_MASK) - (mul >> 16);
return (word16) ((res <=0 ? res+IDEA_MODULO : res) & IDEA_MASK); if (res <= 0)
res += IDEA_MODULO;
return (word16) (res & IDEA_MASK);
} }
if (!x) if (!x)
return (IDEA_MODULO - y); return ((IDEA_MODULO - y) & IDEA_MASK);
/* !y */ /* !y */
return (IDEA_MODULO - x); return ((IDEA_MODULO - x) & IDEA_MASK);
} }
/* compute 1/a modulo 2^16+1 using Extended euclidean algorithm /* compute 1/a modulo 2^16+1 using Extended euclidean algorithm
@@ -98,10 +101,10 @@ static INLINE word16 idea_invmod(word16 x)
v -= u; v -= u;
d -= b; d -= b;
} }
} while (u); } while (u != 0);
/* d is now the inverse, put positive value if required */ /* d is now the inverse, put positive value if required */
if (d < 0) while (d < 0)
d += IDEA_MODULO; d += IDEA_MODULO;
return (word16)(d & IDEA_MASK); return (word16)(d & IDEA_MASK);