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Added v2 for encryption utilities.

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Version 1 derives an encryption key without dependence on OTP.
Version 2 derives an encryption key with dependence on OTP.

Signed-off-by: Pol Henarejos <pol.henarejos@cttc.es>
This commit is contained in:
Pol Henarejos
2026-03-19 18:11:53 +01:00
parent a9ac2779b7
commit 89a8042634
2 changed files with 23 additions and 6 deletions
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24
src/crypto_utils.c
View File

@@ -80,11 +80,19 @@ void pin_derive_kenc(const uint8_t pin_token[32], uint8_t kenc[32]) {
mbedtls_hkdf(SHA256(), pico_serial_hash, sizeof(pico_serial_hash), pin_token, 32, (const uint8_t *)"PIN/ENC", 7, kenc, 32);
}
void pin_derive_kenc2(const uint8_t pin_token[32], uint8_t kenc[32]) {
uint8_t kbase[64];
derive_kbase(kbase);
memcpy(kbase + 32, pin_token, 32);
mbedtls_hkdf(SHA256(), pico_serial_hash, sizeof(pico_serial_hash), kbase, 64, (const uint8_t *)"PIN/ENC2", 8, kenc, 32);
mbedtls_platform_zeroize(kbase, sizeof(kbase));
}
// ------------------------------------------------------------------
// Encrypt 32-byte device key using AES-256-GCM
// Output: [nonce|ciphertext|tag] = 12 + in_len + 16 = 60 bytes
// ------------------------------------------------------------------
int encrypt_with_aad(const uint8_t key[32], const uint8_t *in_buf, size_t in_len, uint8_t *out_buf) {
int encrypt_with_aad(const uint8_t key[32], const uint8_t *in_buf, size_t in_len, uint8_t version, uint8_t *out_buf) {
uint8_t *nonce = out_buf;
uint8_t *ct = out_buf + 12;
uint8_t *tag = out_buf + 12 + in_len;
@@ -94,7 +102,11 @@ int encrypt_with_aad(const uint8_t key[32], const uint8_t *in_buf, size_t in_len
mbedtls_gcm_context gcm;
mbedtls_gcm_init(&gcm);
uint8_t kenc[32];
pin_derive_kenc(key, kenc);
if (version == 2) {
pin_derive_kenc2(key, kenc);
} else {
pin_derive_kenc(key, kenc);
}
int rc = mbedtls_gcm_setkey(&gcm, MBEDTLS_CIPHER_ID_AES, kenc, 256);
mbedtls_platform_zeroize(kenc, sizeof(kenc));
if (rc != 0) {
@@ -111,7 +123,7 @@ int encrypt_with_aad(const uint8_t key[32], const uint8_t *in_buf, size_t in_len
// Input: [nonce|ciphertext|tag] = in_len bytes
// Output: decrypted = in_len - 12 - 16 bytes
// ------------------------------------------------------------------
int decrypt_with_aad(const uint8_t key[32], const uint8_t *in_buf, size_t in_len, uint8_t *out_buf) {
int decrypt_with_aad(const uint8_t key[32], const uint8_t *in_buf, size_t in_len, uint8_t version, uint8_t *out_buf) {
const uint8_t *nonce = in_buf;
const uint8_t *ct = in_buf + 12;
const uint8_t *tag = in_buf + in_len - 16;
@@ -119,7 +131,11 @@ int decrypt_with_aad(const uint8_t key[32], const uint8_t *in_buf, size_t in_len
mbedtls_gcm_context gcm;
mbedtls_gcm_init(&gcm);
uint8_t kenc[32];
pin_derive_kenc(key, kenc);
if (version == 2) {
pin_derive_kenc2(key, kenc);
} else {
pin_derive_kenc(key, kenc);
}
int rc = mbedtls_gcm_setkey(&gcm, MBEDTLS_CIPHER_ID_AES, kenc, 256);
mbedtls_platform_zeroize(kenc, sizeof(kenc));
if (rc != 0) {

5
src/crypto_utils.h
View File

@@ -43,10 +43,11 @@ extern int ct_memcmp(const void *a, const void *b, size_t n);
extern void derive_kbase(uint8_t kbase[32]);
extern void derive_kver(const uint8_t *pin, size_t pin_len, uint8_t kver[32]);
extern void pin_derive_kenc(const uint8_t pin_token[32], uint8_t kenc[32]);
extern void pin_derive_kenc2(const uint8_t pin_token[32], uint8_t kenc[32]);
extern void pin_derive_session(const uint8_t *pin, size_t pin_len, uint8_t pin_token[32]);
extern void pin_derive_verifier(const uint8_t *pin, size_t pin_len, uint8_t verifier[32]);
extern int encrypt_with_aad(const uint8_t key[32], const uint8_t *in_buf, size_t in_len, uint8_t *out_buf);
extern int decrypt_with_aad(const uint8_t key[32], const uint8_t *in_buf, size_t in_len, uint8_t *out_buf);
extern int encrypt_with_aad(const uint8_t key[32], const uint8_t *in_buf, size_t in_len, uint8_t version, uint8_t *out_buf);
extern int decrypt_with_aad(const uint8_t key[32], const uint8_t *in_buf, size_t in_len, uint8_t version, uint8_t *out_buf);
extern void double_hash_pin(const uint8_t *pin, uint16_t len, uint8_t output[32]);
extern void hash_multi(const uint8_t *input, uint16_t len, uint8_t output[32]);
extern void hash256(const uint8_t *input, size_t len, uint8_t output[32]);