29 lines
564 B
C
29 lines
564 B
C
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#include "os.h"
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#include <mp.h>
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#include <libsec.h>
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mpint*
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egdecrypt(EGpriv *priv, mpint *in, mpint *out)
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{
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EGpub *pub = &priv->pub;
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mpint *gamma, *delta;
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mpint *p = pub->p;
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int plen = mpsignif(p)+1;
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int shift = ((plen+Dbits-1)/Dbits)*Dbits;
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if(out == nil)
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out = mpnew(0);
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gamma = mpnew(0);
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delta = mpnew(0);
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mpright(in, shift, gamma);
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mpleft(gamma, shift, delta);
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mpsub(in, delta, delta);
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mpexp(gamma, priv->secret, p, out);
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mpinvert(out, p, gamma);
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mpmul(gamma, delta, out);
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mpmod(out, p, out);
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mpfree(gamma);
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mpfree(delta);
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return out;
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}
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