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rsagen: prefer 65537 as the default exponent when elen == 0, otherwise pick randomly

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This commit is contained in:
cinap_lenrek 2017-02-06 04:25:38 +01:00
parent 5256f4063e
commit bbce9c0566
2 changed files with 8 additions and 4 deletions
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2
sys/src/cmd/auth/rsagen.c
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@ -42,7 +42,7 @@ main(int argc, char **argv)
do{
if(key)
rsaprivfree(key);
key = rsagen(bits, 6, 0);
key = rsagen(bits, 0, 0);
}while(mpsignif(key->pub.n) != bits);
s = smprint("key proto=rsa %s%ssize=%d ek=%B !dk=%B n=%B !p=%B !q=%B !kp=%B !kq=%B !c2=%B\n",

10
sys/src/libsec/port/rsagen.c
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@ -26,9 +26,13 @@ rsagen(int nlen, int elen, int rounds)
// find an e relatively prime to phi
t1 = mpnew(0);
t2 = mpnew(0);
mprand(elen, genrandom, e);
if(mpcmp(e,mptwo) <= 0)
itomp(3, e);
if(elen == 0)
itomp(65537, e);
else {
mprand(elen, genrandom, e);
if(mpcmp(e,mptwo) <= 0)
itomp(3, e);
}
// See Menezes et al. p.291 "8.8 Note (selecting primes)" for discussion
// of the merits of various choices of primes and exponents. e=3 is a
// common and recommended exponent, but doesn't necessarily work here