pub/, progs/: Implement Bernstein's X25519 key-exchange algorithm.

[catacomb] / progs / cc-kem.c

diff --git a/progs/cc-kem.c b/progs/cc-kem.c
index 4a2cf1924c6286eac9b7d8ba6a925254f89ff8a8..71c89e473255268c68e5562105a5b717ae4e8bd4 100644 (file)
--- a/progs/cc-kem.c
+++ b/progs/cc-kem.c
@@ -43,6 +43,7 @@
 #include "ec-keys.h"
 #include "dh.h"
 #include "rsa.h"
+#include "x25519.h"
 
 #include "rmd160.h"
 #include "blowfish-cbc.h"
@@ -602,6 +603,71 @@ static const kemops ec_decops = {
   ec_decinit, dh_decdoit, dh_enccheck, dh_encdestroy
 };
 
+/* --- X25519 --- */
+
+static kem *x25519_encinit(key *k, void *kd) { return (CREATE(kem)); }
+static void x25519_encdestroy(kem *k) { DESTROY(k); }
+
+static const char *x25519_enccheck(kem *k)
+{
+  x25519_pub *kd = k->kd;
+
+  if (kd->pub.sz != X25519_PUBSZ)
+    return ("incorrect X25519 public key length");
+  return (0);
+}
+
+static int x25519_encdoit(kem *k, dstr *d, ghash *h)
+{
+  octet t[X25519_KEYSZ], z[X25519_OUTSZ];
+  x25519_pub *kd = k->kd;
+
+  rand_get(RAND_GLOBAL, t, sizeof(t));
+  dstr_ensure(d, X25519_PUBSZ);
+  x25519((octet *)d->buf, t, x25519_base);
+  x25519(z, t, kd->pub.k);
+  d->len += X25519_PUBSZ;
+  GH_HASH(h, d->buf, X25519_PUBSZ);
+  GH_HASH(h, z, X25519_OUTSZ);
+  return (0);
+}
+
+static const char *x25519_deccheck(kem *k)
+{
+  x25519_priv *kd = k->kd;
+
+  if (kd->priv.sz != X25519_KEYSZ)
+    return ("incorrect X25519 private key length");
+  if (kd->pub.sz != X25519_PUBSZ)
+    return ("incorrect X25519 public key length");
+  return (0);
+}
+
+static int x25519_decdoit(kem *k, dstr *d, ghash *h)
+{
+  octet z[X25519_OUTSZ];
+  x25519_priv *kd = k->kd;
+  int rc = -1;
+
+  if (d->len != X25519_PUBSZ) goto done;
+  x25519(z, kd->priv.k, (const octet *)d->buf);
+  GH_HASH(h, d->buf, X25519_PUBSZ);
+  GH_HASH(h, z, X25519_OUTSZ);
+  rc = 0;
+done:
+  return (rc);
+}
+
+static const kemops x25519_encops = {
+  x25519_pubfetch, sizeof(x25519_pub),
+  x25519_encinit, x25519_encdoit, x25519_enccheck, x25519_encdestroy
+};
+
+static const kemops x25519_decops = {
+  x25519_privfetch, sizeof(x25519_priv),
+  x25519_encinit, x25519_decdoit, x25519_deccheck, x25519_encdestroy
+};
+
 /* --- Symmetric --- */
 
 typedef struct symm_ctx {
@@ -670,6 +736,7 @@ const struct kemtab kemtab[] = {
   { "dh",      &dh_encops,     &dh_decops },
   { "bindh",   &bindh_encops,  &bindh_decops },
   { "ec",      &ec_encops,     &ec_decops },
+  { "x25519",  &x25519_encops, &x25519_decops },
   { "symm",    &symm_encops,   &symm_decops },
   { 0,         0,              0 }
 };