mirror of
https://github.com/trezor/trezor-firmware.git
synced 2024-12-15 02:48:11 +00:00
61 lines
2.4 KiB
C
61 lines
2.4 KiB
C
// Implementations of the XChaCha20 + Poly1305 and ChaCha20 + Poly1305
|
|
// AEAD constructions with a goal of simplicity and correctness rather
|
|
// than performance.
|
|
|
|
#include "chacha20poly1305.h"
|
|
#include "ecrypt-portable.h"
|
|
|
|
void hchacha20(ECRYPT_ctx *x,u8 *c);
|
|
|
|
// Initialize the XChaCha20 + Poly1305 context for encryption or decryption
|
|
// using a 32 byte key and 24 byte nonce. The key and the first 16 bytes of
|
|
// the nonce are used as input to HChaCha20 to derive the Chacha20 key.
|
|
void xchacha20poly1305_init(chacha20poly1305_ctx *ctx, const uint8_t key[32], const uint8_t nonce[24]) {
|
|
unsigned char subkey[32] = {0};
|
|
unsigned char block0[64] = {0};
|
|
ECRYPT_ctx tmp = {0};
|
|
|
|
// Generate the Chacha20 key by applying HChaCha20 to the
|
|
// original key and the first 16 bytes of the nonce.
|
|
ECRYPT_keysetup(&tmp, key, 256, 16);
|
|
tmp.input[12] = U8TO32_LITTLE(nonce + 0);
|
|
tmp.input[13] = U8TO32_LITTLE(nonce + 4);
|
|
tmp.input[14] = U8TO32_LITTLE(nonce + 8);
|
|
tmp.input[15] = U8TO32_LITTLE(nonce + 12);
|
|
hchacha20(&tmp, subkey);
|
|
|
|
// Initialize Chacha20 with the newly generated key and
|
|
// the last 8 bytes of the nonce.
|
|
ECRYPT_keysetup(&ctx->chacha20, subkey, 256, 16);
|
|
ECRYPT_ivsetup(&ctx->chacha20, nonce+16);
|
|
|
|
// Encrypt 64 bytes of zeros and use the first 32 bytes
|
|
// as the Poly1305 key.
|
|
ECRYPT_encrypt_bytes(&ctx->chacha20, block0, block0, 64);
|
|
poly1305_init(&ctx->poly1305, block0);
|
|
}
|
|
|
|
// Encrypt n bytes of plaintext where n must be evenly divisible by the
|
|
// Chacha20 blocksize of 64, except for the final n bytes of plaintext.
|
|
void chacha20poly1305_encrypt(chacha20poly1305_ctx *ctx, const uint8_t *in, uint8_t *out, size_t n) {
|
|
ECRYPT_encrypt_bytes(&ctx->chacha20, in, out, n);
|
|
poly1305_update(&ctx->poly1305, out, n);
|
|
}
|
|
|
|
// Decrypt n bytes of ciphertext where n must be evenly divisible by the
|
|
// Chacha20 blocksize of 64, except for the final n bytes of ciphertext.
|
|
void chacha20poly1305_decrypt(chacha20poly1305_ctx *ctx, const uint8_t *in, uint8_t *out, size_t n) {
|
|
poly1305_update(&ctx->poly1305, in, n);
|
|
ECRYPT_encrypt_bytes(&ctx->chacha20, in, out, n);
|
|
}
|
|
|
|
// Include authenticated data in the Poly1305 MAC.
|
|
void chacha20poly1305_auth(chacha20poly1305_ctx *ctx, const uint8_t *in, size_t n) {
|
|
poly1305_update(&ctx->poly1305, in, n);
|
|
}
|
|
|
|
// Compute NaCl secretbox-style Poly1305 MAC.
|
|
void chacha20poly1305_finish(chacha20poly1305_ctx *ctx, uint8_t mac[16]) {
|
|
poly1305_finish(&ctx->poly1305, mac);
|
|
}
|