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@@ -11,30 +11,43 @@
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#include "key.h"
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#define ECIES_KEY_HASH SHA256
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#define ECIES_KEY_LENGTH (256/8)
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#define ECIES_KEY_TYPE uint256
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#define ECIES_ENC_ALGO EVP_aes_256_cbc()
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#define ECIES_ENC_KEY_SIZE (256/8)
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#define ECIES_ENC_BLK_SIZE (128/8)
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#define ECIES_ENC_KEY_TYPE uint256
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#define ECIES_ENC_IV_TYPE uint128
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#define ECIES_HMAC_ALGO EVP_sha256()
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#define ECIES_HMAC_SIZE (256/8)
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#define ECIES_HMAC_TYPE uint256
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// ECIES uses elliptic curve keys to send an encrypted message.
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static void* ecies_key_derivation(const void *input, size_t ilen, void *output, size_t *olen)
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{ // This function must not be changed as it must be what ECDH_compute_key expects
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if (*olen < ECIES_KEY_LENGTH)
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{
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assert(false);
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return NULL;
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}
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*olen = ECIES_KEY_LENGTH;
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return ECIES_KEY_HASH(static_cast<const unsigned char *>(input), ilen, static_cast<unsigned char *>(output));
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}
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// A shared secret is generated from one public key and one private key.
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// The same key results regardless of which key is public and which private.
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ECIES_KEY_TYPE CKey::getECIESSecret(CKey& otherKey)
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// Anonymous messages can be sent by generating an ephemeral public/private
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// key pair, using that private key with the recipient's public key to
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// encrypt and publishing the ephemeral public key. Non-anonymous messages
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// can be sent by using your own private key with the recipient's public key.
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// A random IV is used to encrypt the message and an HMAC is used to ensure
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// message integrity. If you need timestamps or need to tell the recipient
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// which key to use (his, yours, or ephemeral) you must add that data.
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// (Obviously, key information can't go in the encrypted portion anyway.)
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// Our ciphertext is all encrypted except the IV. The encrypted data decodes as follows:
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// 1) IV (unencrypted)
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// 2) Encrypted: HMAC of original plaintext
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// 3) Encrypted: Original plaintext
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// 4) Encrypted: Rest of block/padding
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// Algorithmic choices:
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#define ECIES_KEY_HASH SHA512 // Hash used to expand shared secret
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#define ECIES_KEY_LENGTH (512/8) // Size of expanded shared secret
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#define ECIES_MIN_SEC (128/8) // The minimum equivalent security
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#define ECIES_ENC_ALGO EVP_aes_256_cbc() // Encryption algorithm
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#define ECIES_ENC_KEY_TYPE uint256 // Type used to hold shared secret
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#define ECIES_ENC_KEY_SIZE (256/8) // Encryption key size
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#define ECIES_ENC_BLK_SIZE (128/8) // Encryption block size
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#define ECIES_ENC_IV_TYPE uint128 // Type used to hold IV
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#define ECIES_HMAC_ALGO EVP_sha256() // HMAC algorithm
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#define ECIES_HMAC_KEY_TYPE uint256 // Type used to hold HMAC key
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#define ECIES_HMAC_KEY_SIZE (256/8) // Size of HMAC key
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#define ECIES_HMAC_TYPE uint256 // Type used to hold HMAC value
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#define ECIES_HMAC_SIZE (256/8) // Size of HMAC value
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void CKey::getECIESSecret(CKey& otherKey, ECIES_ENC_KEY_TYPE& enc_key, ECIES_HMAC_KEY_TYPE& hmac_key)
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{ // Retrieve a secret generated from an EC key pair. At least one private key must be known.
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if(!pkey || !otherKey.pkey)
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throw std::runtime_error("missing key");
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@@ -52,25 +65,27 @@ ECIES_KEY_TYPE CKey::getECIESSecret(CKey& otherKey)
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}
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else throw std::runtime_error("no private key");
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ECIES_KEY_TYPE key;
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if (ECDH_compute_key(key.begin(), ECIES_KEY_LENGTH, EC_KEY_get0_public_key(pubkey),
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privkey, ecies_key_derivation) != ECIES_KEY_LENGTH)
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unsigned char rawbuf[512];
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int buflen=ECDH_compute_key(rawbuf, 512, EC_KEY_get0_public_key(pubkey), privkey, NULL);
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if(buflen < ECIES_MIN_SEC)
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throw std::runtime_error("ecdh key failed");
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return key;
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unsigned char hbuf[ECIES_KEY_LENGTH];
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ECIES_KEY_HASH(rawbuf, buflen, hbuf);
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memset(rawbuf, 0, ECIES_HMAC_KEY_SIZE);
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assert((ECIES_ENC_KEY_SIZE + ECIES_HMAC_KEY_SIZE) >= ECIES_KEY_LENGTH);
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memcpy(enc_key.begin(), hbuf, ECIES_ENC_KEY_SIZE);
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memcpy(hmac_key.begin(), hbuf + ECIES_ENC_KEY_SIZE, ECIES_HMAC_KEY_SIZE);
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memset(hbuf, 0, ECIES_KEY_LENGTH);
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}
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// Our ciphertext is all encrypted except the IV. The encrypted data decodes as follows:
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// 1) IV (unencrypted)
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// 2) Encrypted: HMAC of original plaintext
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// 3) Encrypted: Original plaintext
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// 4) Encrypted: Rest of block/padding
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static ECIES_HMAC_TYPE makeHMAC(ECIES_KEY_TYPE secret, const std::vector<unsigned char> data)
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static ECIES_HMAC_TYPE makeHMAC(const ECIES_HMAC_KEY_TYPE& secret, const std::vector<unsigned char> data)
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{
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HMAC_CTX ctx;
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HMAC_CTX_init(&ctx);
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if(HMAC_Init_ex(&ctx, secret.begin(), ECIES_KEY_LENGTH, ECIES_HMAC_ALGO, NULL) != 1)
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if(HMAC_Init_ex(&ctx, secret.begin(), ECIES_HMAC_KEY_SIZE, ECIES_HMAC_ALGO, NULL) != 1)
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{
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HMAC_CTX_cleanup(&ctx);
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throw std::runtime_error("init hmac");
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@@ -82,37 +97,42 @@ static ECIES_HMAC_TYPE makeHMAC(ECIES_KEY_TYPE secret, const std::vector<unsigne
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throw std::runtime_error("update hmac");
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}
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unsigned int ml=EVP_MAX_MD_SIZE;
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std::vector<unsigned char> hmac(ml);
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if(HMAC_Final(&ctx, &(hmac.front()), &ml) != 1)
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ECIES_HMAC_TYPE ret;
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unsigned int ml = ECIES_HMAC_SIZE;
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if(HMAC_Final(&ctx, ret.begin(), &ml) != 1)
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{
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HMAC_CTX_cleanup(&ctx);
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throw std::runtime_error("finalize hmac");
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}
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ECIES_HMAC_TYPE ret;
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memcpy(ret.begin(), &(hmac.front()), ECIES_HMAC_SIZE);
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assert(ml == ECIES_HMAC_SIZE);
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HMAC_CTX_cleanup(&ctx);
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return ret;
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}
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std::vector<unsigned char> CKey::encryptECIES(CKey& otherKey, const std::vector<unsigned char>& plaintext)
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{
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ECIES_KEY_TYPE secret=getECIESSecret(otherKey);
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ECIES_HMAC_TYPE hmac=makeHMAC(secret, plaintext);
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ECIES_ENC_IV_TYPE iv;
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if(RAND_bytes(static_cast<unsigned char *>(iv.begin()), ECIES_ENC_BLK_SIZE) != 1)
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throw std::runtime_error("insufficient entropy");
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ECIES_ENC_KEY_TYPE secret;
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ECIES_HMAC_KEY_TYPE hmacKey;
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getECIESSecret(otherKey, secret, hmacKey);
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ECIES_HMAC_TYPE hmac=makeHMAC(hmacKey, plaintext);
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hmacKey.zero();
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EVP_CIPHER_CTX ctx;
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EVP_CIPHER_CTX_init(&ctx);
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if (EVP_EncryptInit_ex(&ctx, ECIES_ENC_ALGO, NULL, secret.begin(), iv.begin()) != 1)
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{
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EVP_CIPHER_CTX_cleanup(&ctx);
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secret.zero();
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throw std::runtime_error("init cipher ctx");
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}
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secret.zero();
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std::vector<unsigned char> out(plaintext.size() + ECIES_HMAC_SIZE + ECIES_ENC_KEY_SIZE + ECIES_ENC_BLK_SIZE, 0);
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int len=0, bytesWritten;
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@@ -160,10 +180,9 @@ std::vector<unsigned char> CKey::encryptECIES(CKey& otherKey, const std::vector<
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std::vector<unsigned char> CKey::decryptECIES(CKey& otherKey, const std::vector<unsigned char>& ciphertext)
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{
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ECIES_KEY_TYPE secret=getECIESSecret(otherKey);
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// minimum ciphertext = IV + HMAC + 1 block
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if(ciphertext.size() < ((2*ECIES_ENC_BLK_SIZE) + ECIES_HMAC_SIZE) )
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if(ciphertext.size() < ((2 * ECIES_ENC_BLK_SIZE) + ECIES_HMAC_SIZE) )
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throw std::runtime_error("ciphertext too short");
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// extract IV
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@@ -173,9 +192,14 @@ std::vector<unsigned char> CKey::decryptECIES(CKey& otherKey, const std::vector<
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// begin decrypting
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EVP_CIPHER_CTX ctx;
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EVP_CIPHER_CTX_init(&ctx);
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ECIES_ENC_KEY_TYPE secret;
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ECIES_HMAC_KEY_TYPE hmacKey;
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getECIESSecret(otherKey, secret, hmacKey);
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if(EVP_DecryptInit_ex(&ctx, ECIES_ENC_ALGO, NULL, secret.begin(), iv.begin()) != 1)
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{
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secret.zero();
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hmacKey.zero();
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EVP_CIPHER_CTX_cleanup(&ctx);
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throw std::runtime_error("unable to init cipher");
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}
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@@ -184,8 +208,10 @@ std::vector<unsigned char> CKey::decryptECIES(CKey& otherKey, const std::vector<
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ECIES_HMAC_TYPE hmac;
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int outlen=ECIES_HMAC_SIZE;
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if( (EVP_DecryptUpdate(&ctx, hmac.begin(), &outlen,
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&(ciphertext.front()) + ECIES_ENC_BLK_SIZE, ECIES_HMAC_SIZE+1) != 1) || (outlen != ECIES_HMAC_SIZE) )
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&(ciphertext.front()) + ECIES_ENC_BLK_SIZE, ECIES_HMAC_SIZE + 1) != 1) || (outlen != ECIES_HMAC_SIZE) )
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{
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secret.zero();
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hmacKey.zero();
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EVP_CIPHER_CTX_cleanup(&ctx);
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throw std::runtime_error("unable to extract hmac");
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}
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@@ -194,26 +220,36 @@ std::vector<unsigned char> CKey::decryptECIES(CKey& otherKey, const std::vector<
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std::vector<unsigned char> plaintext(ciphertext.size() - ECIES_HMAC_SIZE - ECIES_ENC_BLK_SIZE);
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outlen=plaintext.size();
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if(EVP_DecryptUpdate(&ctx, &(plaintext.front()), &outlen,
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&(ciphertext.front())+ECIES_ENC_BLK_SIZE+ECIES_HMAC_SIZE+1,
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ciphertext.size()-ECIES_ENC_BLK_SIZE-ECIES_HMAC_SIZE-1) != 1)
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&(ciphertext.front()) + ECIES_ENC_BLK_SIZE + ECIES_HMAC_SIZE + 1,
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ciphertext.size() - ECIES_ENC_BLK_SIZE - ECIES_HMAC_SIZE - 1) != 1)
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{
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secret.zero();
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hmacKey.zero();
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EVP_CIPHER_CTX_cleanup(&ctx);
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throw std::runtime_error("unable to extract plaintext");
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}
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// decrypt padding
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int flen = 0;
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if(EVP_DecryptFinal(&ctx, &(plaintext.front()) + outlen, &flen) != 1)
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{
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secret.zero();
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hmacKey.zero();
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EVP_CIPHER_CTX_cleanup(&ctx);
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throw std::runtime_error("plaintext had bad padding");
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}
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plaintext.resize(flen + outlen);
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if(hmac != makeHMAC(secret, plaintext))
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// verify integrity
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if(hmac != makeHMAC(hmacKey, plaintext))
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{
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secret.zero();
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hmacKey.zero();
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EVP_CIPHER_CTX_cleanup(&ctx);
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throw std::runtime_error("plaintext had bad hmac");
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}
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secret.zero();
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hmacKey.zero();
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EVP_CIPHER_CTX_cleanup(&ctx);
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return plaintext;
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@@ -222,19 +258,25 @@ std::vector<unsigned char> CKey::decryptECIES(CKey& otherKey, const std::vector<
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bool checkECIES(void)
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{
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CKey senderPriv, recipientPriv, senderPub, recipientPub;
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senderPriv.MakeNewKey();
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recipientPriv.MakeNewKey();
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if(!senderPub.SetPubKey(senderPriv.GetPubKey()))
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throw std::runtime_error("key error");
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if(!recipientPub.SetPubKey(recipientPriv.GetPubKey()))
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throw std::runtime_error("key error");
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for(int i=0; i<30000; i++)
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{
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if((i%100)==0)
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{ // generate new keys every 100 times
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// std::cerr << "new keys" << std::endl;
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senderPriv.MakeNewKey();
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recipientPriv.MakeNewKey();
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if(!senderPub.SetPubKey(senderPriv.GetPubKey()))
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throw std::runtime_error("key error");
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if(!recipientPub.SetPubKey(recipientPriv.GetPubKey()))
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throw std::runtime_error("key error");
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}
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// generate message
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std::vector<unsigned char> message(4096);
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int msglen=i%3000;
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if(RAND_bytes(static_cast<unsigned char *>(&message.front()), msglen) != 1)
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throw std::runtime_error("insufficient entropy");
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message.resize(msglen);
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@@ -245,7 +287,11 @@ bool checkECIES(void)
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// decrypt message with recipient's private key and sender's public key
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std::vector<unsigned char> decrypt=recipientPriv.decryptECIES(senderPub, ciphertext);
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if(decrypt != message) return false;
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if(decrypt != message)
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{
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assert(false);
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return false;
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}
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// std::cerr << "Msg(" << msglen << ") ok " << ciphertext.size() << std::endl;
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}
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|
|
|
|
return true;
|
|
|
|
|
|