diff options
| -rw-r--r-- | src/cryptech_novena_i2c_trng.c (renamed from src/cryptech_novena_i2c_entropy.c) | 39 |
1 files changed, 24 insertions, 15 deletions
diff --git a/src/cryptech_novena_i2c_entropy.c b/src/cryptech_novena_i2c_trng.c index b2e6e22..599c0db 100644 --- a/src/cryptech_novena_i2c_entropy.c +++ b/src/cryptech_novena_i2c_trng.c @@ -1,11 +1,11 @@ /* - * cryptech_novena_i2c_entropy.c + * cryptech_novena_i2c_trng.c * ------------------------------ * * This is an early prototype Hardware Adaption Layer (HAL) for using * Cryptlib with the Cryptech project's FGPA cores over an I2C bus on * the Novena PVT1 development board using the "coretest" byte stream - * protocol. This is compatible with the test/novena_entropy FPGA build. + * protocol. This is compatible with the test/novena_trng FPGA build. * * The communication channel used here is not suitable for production * use, this is just a prototype. @@ -111,12 +111,12 @@ /* * Address for reading 32 bits of entropy from the noise board. - * ENTROPY_VALID is nonzero if there's valid entropy available. + * TRNG_VALID is nonzero if valid random bits are available. */ -#define ENTROPY_PREFIX 0x20 -#define ENTROPY_ADDR 0x20 -#define ENTROPY_VALID 0x11 +#define TRNG_PREFIX 0x0b +#define TRNG_DATA 0x20 +#define TRNG_VALID 0x11 static int i2cfd = -1; static int debug = 0; @@ -363,9 +363,14 @@ static int i2c_wait_valid(const unsigned char addr0) /* * First attempt at reading random data from the Novena. - * Not sure what we should do if ENTROPY_VALID isn't lit, spin wait? + * + * In theory, we should wait for TRNG_VALID before reading random + * data, but as long as this is running over I2C we're going to be so + * slow that there's no point, and checking would just make us slower. */ +#define WAIT_FOR_TRNG_VALID 0 + static int readRandom(void *buffer, const int length) { unsigned char temp[4], *buf = buffer; @@ -376,23 +381,27 @@ static int readRandom(void *buffer, const int length) REQUIRES_B(length >= 1 && length < MAX_INTLENGTH); for (i = 0; i < length; i += 4) { - if (!i2c_wait_valid(ENTROPY_PREFIX)) { - fprintf(stderr, "[ i2c_wait_valid(ENTROPY_PREFIX) failed ]\n"); + +#if WAIT_FOR_TRNG_VALID + if (!i2c_wait_valid(TRNG_PREFIX)) { + fprintf(stderr, "[ i2c_wait_valid(TRNG_PREFIX) failed ]\n"); return 0; } do { - if (!i2c_read(ENTROPY_PREFIX, ENTROPY_VALID, temp)) { - fprintf(stderr, "[ i2c_read(ENTROPY_VALID) failed ]\n"); + if (!i2c_read(TRNG_PREFIX, TRNG_VALID, temp)) { + fprintf(stderr, "[ i2c_read(TRNG_VALID) failed ]\n"); return 0; } } while (!temp[3]); - if (!i2c_wait_valid(ENTROPY_PREFIX)) { - fprintf(stderr, "[ i2c_wait_valid(ENTROPY_PREFIX) failed ]\n"); + if (!i2c_wait_valid(TRNG_PREFIX)) { + fprintf(stderr, "[ i2c_wait_valid(TRNG_PREFIX) failed ]\n"); return 0; } +#endif /* WAIT_FOR_TRNG_VALID */ + last = (length - i) < 4; - if (!i2c_read(ENTROPY_PREFIX, ENTROPY_ADDR, last ? temp : buf + i)) { - fprintf(stderr, "[ i2c_read(ENTROPY_ADDR) failed ]\n"); + if (!i2c_read(TRNG_PREFIX, TRNG_DATA, (last ? temp : (buf + i)))) { + fprintf(stderr, "[ i2c_read(TRNG_DATA) failed ]\n"); return 0; } if (last) { |