diff options
| author | Keith Packard <keithp@keithp.com> | 2016-08-02 16:26:49 -0700 |
|---|---|---|
| committer | Keith Packard <keithp@keithp.com> | 2016-08-02 16:55:11 -0700 |
| commit | 826ad792389150ea8d80e341cb8ea023db83c9a2 (patch) | |
| tree | 3cd1aba84ec58761c4d3374a9386177a9dc4e6a2 /src/drivers/ao_trng_send.c | |
| parent | 1934468e96ea9d179abf6e3e728b6b14ce793f46 (diff) | |
altos: Use standard FIPS testing for chaoskey
Check to make sure we aren't repeating a block coming from the
unwhitened source, which is the standard online FIPS test for RNGs.
Signed-off-by: Keith Packard <keithp@keithp.com>
Diffstat (limited to 'src/drivers/ao_trng_send.c')
| -rw-r--r-- | src/drivers/ao_trng_send.c | 30 |
1 files changed, 7 insertions, 23 deletions
diff --git a/src/drivers/ao_trng_send.c b/src/drivers/ao_trng_send.c index 00efa8d9..85034efd 100644 --- a/src/drivers/ao_trng_send.c +++ b/src/drivers/ao_trng_send.c @@ -97,18 +97,7 @@ ao_trng_send_raw(void) #endif -/* Make sure there's at least 8 bits of variance in the samples */ -#define MIN_VARIANCE (128 * 128) - -/* Make sure the signal is spread around a bit */ -#define MAX_VARIANCE (512 * 512) - -#define ADD_STATS(value) do { \ - sum += (value); \ - sum2 += (value) * (value); \ - } while(0) - -#define VARIANCE(n) ((sum2 - (sum / (n) * sum)) / (n)) +static uint32_t previous[AO_USB_IN_SIZE / sizeof (uint16_t)]; static int ao_trng_get_cooked(uint16_t *buf) @@ -116,29 +105,24 @@ ao_trng_get_cooked(uint16_t *buf) uint16_t i; uint16_t t; uint32_t *rnd = (uint32_t *) ao_adc_ring; - int32_t sum, sum2, var; + uint8_t mismatch = 0; - sum = sum2 = 0; t = ao_adc_get(AO_USB_IN_SIZE) >> 1; /* one 16-bit value per output byte */ for (i = 0; i < AO_USB_IN_SIZE / sizeof (uint16_t); i++) { uint32_t v; - uint16_t v1, v2; /* Fetch two values in one operation */ v = rnd[t]; + if (v != previous[i]) { + mismatch = 1; + previous[i] = v; + } t = (t + 1) & ((AO_ADC_RING_SIZE >> 1) - 1); *buf++ = ao_crc_in_32_out_16(v); - - v1 = v; - v2 = v >> 16; - - ADD_STATS(v1); - ADD_STATS(v2); } ao_adc_ack(AO_USB_IN_SIZE); - var = VARIANCE(2 * AO_USB_IN_SIZE / sizeof (uint16_t)); - return var >= MIN_VARIANCE && var <= MAX_VARIANCE; + return mismatch; } #define AO_TRNG_START_WAIT 1024 |