Add most of libsec.
diff --git a/src/libsec/port/genstrongprime.c b/src/libsec/port/genstrongprime.c
new file mode 100644
index 0000000..27c43a9
--- /dev/null
+++ b/src/libsec/port/genstrongprime.c
@@ -0,0 +1,57 @@
+#include "os.h"
+#include <mp.h>
+#include <libsec.h>
+
+// Gordon's algorithm for generating a strong prime
+// Menezes et al () Handbook, p.150
+void
+genstrongprime(mpint *p, int n, int accuracy)
+{
+ mpint *s, *t, *r, *i;
+
+ if(n < 64)
+ n = 64;
+
+ s = mpnew(n/2);
+ genprime(s, (n/2)-16, accuracy);
+ t = mpnew(n/2);
+ genprime(t, n-mpsignif(s)-32, accuracy);
+
+ // first r = 2it + 1 that's prime
+ i = mpnew(16);
+ r = mpnew(0);
+ itomp(0x8000, i);
+ mpleft(t, 1, t); // 2t
+ mpmul(i, t, r); // 2it
+ mpadd(r, mpone, r); // 2it + 1
+ for(;;){
+ if(probably_prime(r, 18))
+ break;
+ mpadd(r, t, r); // r += 2t
+ }
+
+ // p0 = 2(s**(r-2) mod r)s - 1
+ itomp(2, p);
+ mpsub(r, p, p);
+ mpexp(s, p, r, p);
+ mpmul(s, p, p);
+ mpleft(p, 1, p);
+ mpsub(p, mpone, p);
+
+ // first p = p0 + 2irs that's prime
+ itomp(0x8000, i);
+ mpleft(r, 1, r); // 2r
+ mpmul(r, s, r); // 2rs
+ mpmul(r, i, i); // 2irs
+ mpadd(p, i, p); // p0 + 2irs
+ for(;;){
+ if(probably_prime(p, accuracy))
+ break;
+ mpadd(p, r, p); // p += 2rs
+ }
+
+ mpfree(i);
+ mpfree(s);
+ mpfree(r);
+ mpfree(t);
+}
