1*8ccd4a63SDavid du Colombier #include "os.h"
2*8ccd4a63SDavid du Colombier #include <mp.h>
3*8ccd4a63SDavid du Colombier #include <libsec.h>
4*8ccd4a63SDavid du Colombier
5*8ccd4a63SDavid du Colombier mpint*
egdecrypt(EGpriv * priv,mpint * in,mpint * out)6*8ccd4a63SDavid du Colombier egdecrypt(EGpriv *priv, mpint *in, mpint *out)
7*8ccd4a63SDavid du Colombier {
8*8ccd4a63SDavid du Colombier EGpub *pub = &priv->pub;
9*8ccd4a63SDavid du Colombier mpint *gamma, *delta;
10*8ccd4a63SDavid du Colombier mpint *p = pub->p;
11*8ccd4a63SDavid du Colombier int plen = mpsignif(p)+1;
12*8ccd4a63SDavid du Colombier int shift = ((plen+Dbits-1)/Dbits)*Dbits;
13*8ccd4a63SDavid du Colombier
14*8ccd4a63SDavid du Colombier if(out == nil)
15*8ccd4a63SDavid du Colombier out = mpnew(0);
16*8ccd4a63SDavid du Colombier gamma = mpnew(0);
17*8ccd4a63SDavid du Colombier delta = mpnew(0);
18*8ccd4a63SDavid du Colombier mpright(in, shift, gamma);
19*8ccd4a63SDavid du Colombier mpleft(gamma, shift, delta);
20*8ccd4a63SDavid du Colombier mpsub(in, delta, delta);
21*8ccd4a63SDavid du Colombier mpexp(gamma, priv->secret, p, out);
22*8ccd4a63SDavid du Colombier mpinvert(out, p, gamma);
23*8ccd4a63SDavid du Colombier mpmul(gamma, delta, out);
24*8ccd4a63SDavid du Colombier mpmod(out, p, out);
25*8ccd4a63SDavid du Colombier mpfree(gamma);
26*8ccd4a63SDavid du Colombier mpfree(delta);
27*8ccd4a63SDavid du Colombier return out;
28*8ccd4a63SDavid du Colombier }
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