Move key-generation code into its own subdir.

Including mpunsafe.{h,c}, which should be an extra defence against
inadvertently using it outside the keygen library.

keygen/ecdsa.c

@@ -0,0 +1,37 @@
+/*
+ * EC key generation.
+ */
+
+#include "ssh.h"
+#include "sshkeygen.h"
+#include "mpint.h"
+
+int ecdsa_generate(struct ecdsa_key *ek, int bits)
+{
+    if (!ec_nist_alg_and_curve_by_bits(bits, &ek->curve, &ek->sshk.vt))
+        return 0;
+
+    mp_int *one = mp_from_integer(1);
+    ek->privateKey = mp_random_in_range(one, ek->curve->w.G_order);
+    mp_free(one);
+
+    ek->publicKey = ecdsa_public(ek->privateKey, ek->sshk.vt);
+
+    return 1;
+}
+
+int eddsa_generate(struct eddsa_key *ek, int bits)
+{
+    if (!ec_ed_alg_and_curve_by_bits(bits, &ek->curve, &ek->sshk.vt))
+        return 0;
+
+    /* EdDSA secret keys are just 32 bytes of hash preimage; the
+     * 64-byte SHA-512 hash of that key will be used when signing,
+     * but the form of the key stored on disk is the preimage
+     * only. */
+    ek->privateKey = mp_random_bits(bits);
+
+    ek->publicKey = eddsa_public(ek->privateKey, ek->sshk.vt);
+
+    return 1;
+}