初始版本

external/cifra_AES128-EAX/eax.c

@@ -0,0 +1,115 @@
+/*
+ * cifra - embedded cryptography library
+ * Written in 2014 by Joseph Birr-Pixton <jpixton@gmail.com>
+ *
+ * To the extent possible under law, the author(s) have dedicated all
+ * copyright and related and neighboring rights to this software to the
+ * public domain worldwide. This software is distributed without any
+ * warranty.
+ *
+ * You should have received a copy of the CC0 Public Domain Dedication
+ * along with this software. If not, see
+ * <http://creativecommons.org/publicdomain/zero/1.0/>.
+ */
+
+#include "prp.h"
+#include "modes.h"
+#include "tassert.h"
+#include "handy.h"
+#include <string.h>
+
+static void cmac_compute_n(cf_cmac_stream *ctx,
+                           uint8_t t,
+                           const uint8_t *input, size_t ninput,
+                           uint8_t out[CF_MAXBLOCK])
+{
+  size_t blocksz = ctx->cmac.prp->blocksz;
+  assert(blocksz > 0);
+
+  uint8_t firstblock[CF_MAXBLOCK];
+  memset(firstblock, 0, blocksz);
+  firstblock[blocksz - 1] = t;
+
+  cf_cmac_stream_reset(ctx);
+  if (ninput)
+  {
+    cf_cmac_stream_update(ctx, firstblock, blocksz, 0);
+    cf_cmac_stream_update(ctx, input, ninput, 1);
+  } else {
+    cf_cmac_stream_update(ctx, firstblock, blocksz, 1);
+  }
+
+  cf_cmac_stream_final(ctx, out);
+}
+
+void cf_eax_encrypt(const cf_prp *prp, void *prpctx,
+                    const uint8_t *plain, size_t nplain,
+                    const uint8_t *header, size_t nheader,
+                    const uint8_t *nonce, size_t nnonce,
+                    uint8_t *cipher, /* the same size as nplain */
+                    uint8_t *tag, size_t ntag)
+{
+  uint8_t NN[CF_MAXBLOCK],
+          HH[CF_MAXBLOCK],
+          CC[CF_MAXBLOCK];
+
+  cf_cmac_stream cmac;
+  cf_cmac_stream_init(&cmac, prp, prpctx);
+
+  /* NN = OMAC_K^0(N) */
+  cmac_compute_n(&cmac, 0, nonce, nnonce, NN);
+
+  /* HH = OMAC_K^1(H) */
+  cmac_compute_n(&cmac, 1, header, nheader, HH);
+
+  /* C = CTR_K^NN(M) */
+  cf_ctr ctr;
+  cf_ctr_init(&ctr, prp, prpctx, NN);
+  cf_ctr_cipher(&ctr, plain, cipher, nplain);
+
+  /* CC = OMAC_K^2(C) */
+  cmac_compute_n(&cmac, 2, cipher, nplain, CC);
+
+  /* Tag = NN ^ CC ^ HH
+   * T = Tag [ first tau bits ] */
+  assert(ntag <= prp->blocksz);
+  for (size_t i = 0; i < ntag; i++)
+    tag[i] = NN[i] ^ CC[i] ^ HH[i];
+}
+
+int cf_eax_decrypt(const cf_prp *prp, void *prpctx,
+                   const uint8_t *cipher, size_t ncipher,
+                   const uint8_t *header, size_t nheader,
+                   const uint8_t *nonce, size_t nnonce,
+                   const uint8_t *tag, size_t ntag,
+                   uint8_t *plain) /* the same size as ncipher */
+{
+  uint8_t NN[CF_MAXBLOCK],
+          HH[CF_MAXBLOCK],
+          CC[CF_MAXBLOCK];
+
+  cf_cmac_stream cmac;
+  cf_cmac_stream_init(&cmac, prp, prpctx);
+
+  /* NN = OMAC_K^0(N) */
+  cmac_compute_n(&cmac, 0, nonce, nnonce, NN);
+
+  /* HH = OMAC_K^1(H) */
+  cmac_compute_n(&cmac, 1, header, nheader, HH);
+
+  /* CC = OMAC_K^2(C) */
+  cmac_compute_n(&cmac, 2, cipher, ncipher, CC);
+
+  uint8_t tt[CF_MAXBLOCK];
+  assert(ntag && ntag <= prp->blocksz);
+  for (size_t i = 0; i < ntag; i++)
+    tt[i] = NN[i] ^ CC[i] ^ HH[i];
+
+  if (!mem_eq(tt, tag, ntag))
+    return 1;
+
+  cf_ctr ctr;
+  cf_ctr_init(&ctr, prp, prpctx, NN);
+  cf_ctr_cipher(&ctr, cipher, plain, ncipher);
+  return 0;
+}