1 files changed, 92 insertions, 0 deletions
diff --git a/crypto.h b/crypto.h
new file mode 100644
index 0000000..67055f7
--- /dev/null
+++ b/crypto.h
@@ -0,0 +1,92 @@
+/*
+  This file is part of msr.
+
+  msr is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+  
+  msr is distributed in the hope that it will be useful, but WITHOUT
+  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+  or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
+  License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with Foobar. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+#pragma pack(1) // VERY IMPORTANT
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <sodium.h>
+
+#include "utils.h"
+
+// --- Algorithm choices ---
+#define SIG_ALG "Ed"
+#define KDF_ALG "Sc"
+#define CHK_ALG "B2"
+
+// --- Widths for various fields in the structs ---
+#define SIG_ALG_WIDTH 2
+#define KDF_ALG_WIDTH 2
+#define CHK_ALG_WIDTH 2
+#define KEY_ID_WIDTH 8
+#define SIG_WIDTH (size_t)crypto_sign_BYTES
+#define CHK_WIDTH (size_t)crypto_generichash_BYTES
+#define SEC_KEY_WIDTH (size_t)crypto_sign_SECRETKEYBYTES
+#define PUB_KEY_WIDTH (size_t)crypto_sign_PUBLICKEYBYTES
+#define KDF_SALT_WIDTH (size_t)crypto_pwhash_scryptsalsa208sha256_SALTBYTES
+#define ENCRYPTED_KEY_WIDTH (KEY_ID_WIDTH + SEC_KEY_WIDTH + CHK_WIDTH)
+
+#define PUB_KEY_STORE_WIDTH sizeof(struct public_key_s)
+#define SEC_KEY_STORE_WIDTH sizeof(struct secret_key_s)
+#define SIGNED_MSG_WIDTH (SIG_ALG_WIDTH+KEY_ID_WIDTH+SIG_WIDTH)
+
+// --- Structs for secret key, public key and messages ---
+typedef struct secret_key_s {
+  uint8_t sig_alg[SIG_ALG_WIDTH];
+  uint8_t kdf_alg[KDF_ALG_WIDTH];
+  uint8_t chk_alg[CHK_ALG_WIDTH];
+  uint8_t kdf_salt[KDF_SALT_WIDTH];
+  uint64_t kdf_opslimit;
+  uint64_t kdf_memlimit;
+  // Below this line is essentially "keynum_sk"
+  // We encrypt for security
+  uint8_t key_id[KEY_ID_WIDTH];
+  uint8_t secret_key[SEC_KEY_WIDTH];
+  uint8_t checksum[CHK_WIDTH];
+} * SecretKey;
+
+typedef struct public_key_s {
+  uint8_t sig_alg[SIG_ALG_WIDTH];
+  uint8_t key_id[KEY_ID_WIDTH];
+  uint8_t public_key[PUB_KEY_WIDTH];
+} * PublicKey;
+
+typedef struct signed_msg_s {
+  uint8_t sig_alg[SIG_ALG_WIDTH];
+  uint8_t key_id[KEY_ID_WIDTH];
+  uint8_t sig[SIG_WIDTH];
+  size_t msglen;
+  uint8_t *msg;
+} * SignedMsg;
+
+// --- Functions ---
+Error generate_key_pair(SecretKey *sk, PublicKey *pk);
+
+Error is_valid_sigmsg(SignedMsg sm);
+Error is_valid_pubkey(PublicKey pk);
+Error is_correct_options(SecretKey sk);
+Error is_correct_checksum(SecretKey sk);
+
+Error alter_seckey(char encrypt, SecretKey sk,
+                   const uint8_t * const passwd,
+                   unsigned long long pwlen);
+
+Error verify_message(PublicKey pk, SignedMsg sm);
+
+Error sign_message(SecretKey sk, SignedMsg sm);