1 #include "os.h"
2 #include <mp.h>
3 #include <libsec.h>
4
5 mpint*
egdecrypt(EGpriv * priv,mpint * in,mpint * out)6 egdecrypt(EGpriv *priv, mpint *in, mpint *out)
7 {
8 EGpub *pub = &priv->pub;
9 mpint *gamma, *delta;
10 mpint *p = pub->p;
11 int plen = mpsignif(p)+1;
12 int shift = ((plen+Dbits-1)/Dbits)*Dbits;
13
14 if(out == nil)
15 out = mpnew(0);
16 gamma = mpnew(0);
17 delta = mpnew(0);
18 mpright(in, shift, gamma);
19 mpleft(gamma, shift, delta);
20 mpsub(in, delta, delta);
21 mpexp(gamma, priv->secret, p, out);
22 mpinvert(out, p, gamma);
23 mpmul(gamma, delta, out);
24 mpmod(out, p, out);
25 mpfree(gamma);
26 mpfree(delta);
27 return out;
28 }
29