crypto: jitter - Allow configuration of oversampling rate

[sfrench/cifs-2.6.git] / crypto / Kconfig

diff --git a/crypto/Kconfig b/crypto/Kconfig
index 00c827d9f0d2de95e5a07f38c2a5d6b9337b774d..ed931ddea644d2c8ddec250965383bbd66a486f5 100644 (file)
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -1339,6 +1339,23 @@ config CRYPTO_JITTERENTROPY_MEMORY_BLOCKSIZE
        default 1024 if CRYPTO_JITTERENTROPY_MEMSIZE_1024
        default 2048 if CRYPTO_JITTERENTROPY_MEMSIZE_8192
 
+config CRYPTO_JITTERENTROPY_OSR
+       int "CPU Jitter RNG Oversampling Rate"
+       range 1 15
+       default 1
+       depends on CRYPTO_JITTERENTROPY
+       help
+         The Jitter RNG allows the specification of an oversampling rate (OSR).
+         The Jitter RNG operation requires a fixed amount of timing
+         measurements to produce one output block of random numbers. The
+         OSR value is multiplied with the amount of timing measurements to
+         generate one output block. Thus, the timing measurement is oversampled
+         by the OSR factor. The oversampling allows the Jitter RNG to operate
+         on hardware whose timers deliver limited amount of entropy (e.g.
+         the timer is coarse) by setting the OSR to a higher value. The
+         trade-off, however, is that the Jitter RNG now requires more time
+         to generate random numbers.
+
 config CRYPTO_JITTERENTROPY_TESTINTERFACE
        bool "CPU Jitter RNG Test Interface"
        depends on CRYPTO_JITTERENTROPY