Add most of libsec.
diff --git a/src/libsec/port/egdecrypt.c b/src/libsec/port/egdecrypt.c
new file mode 100644
index 0000000..2457880
--- /dev/null
+++ b/src/libsec/port/egdecrypt.c
@@ -0,0 +1,28 @@
+#include "os.h"
+#include <mp.h>
+#include <libsec.h>
+
+mpint*
+egdecrypt(EGpriv *priv, mpint *in, mpint *out)
+{
+ EGpub *pub = &priv->pub;
+ mpint *gamma, *delta;
+ mpint *p = pub->p;
+ int plen = mpsignif(p)+1;
+ int shift = ((plen+Dbits-1)/Dbits)*Dbits;
+
+ if(out == nil)
+ out = mpnew(0);
+ gamma = mpnew(0);
+ delta = mpnew(0);
+ mpright(in, shift, gamma);
+ mpleft(gamma, shift, delta);
+ mpsub(in, delta, delta);
+ mpexp(gamma, priv->secret, p, out);
+ mpinvert(out, p, gamma);
+ mpmul(gamma, delta, out);
+ mpmod(out, p, out);
+ mpfree(gamma);
+ mpfree(delta);
+ return out;
+}
