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authorlloyd <[email protected]>2012-02-15 16:53:08 +0000
committerlloyd <[email protected]>2012-02-15 16:53:08 +0000
commit718d9503e3bad05fa58d61af11784976a495e21a (patch)
tree8724b0002fc444ea5e6d9703656cd827052abc67 /src/rng/hmac_rng/hmac_rng.cpp
parent88626b546863966ba6cf100d68fb9d73bc2a9fb9 (diff)
Force a reseed in HMAC_RNG after 20 bytes have been added, rather than
waiting for a full kilobyte. This is for the benefit of DSA/ECDSA which want a call to add_entropy to update the state in some way, passing just a hash input which might be as small as 20 bytes.
Diffstat (limited to 'src/rng/hmac_rng/hmac_rng.cpp')
-rw-r--r--src/rng/hmac_rng/hmac_rng.cpp17
1 files changed, 12 insertions, 5 deletions
diff --git a/src/rng/hmac_rng/hmac_rng.cpp b/src/rng/hmac_rng/hmac_rng.cpp
index 7912e58af..55503382a 100644
--- a/src/rng/hmac_rng/hmac_rng.cpp
+++ b/src/rng/hmac_rng/hmac_rng.cpp
@@ -110,7 +110,11 @@ void HMAC_RNG::reseed(size_t poll_bits)
counter = 0;
user_input_len = 0;
- if(accum.bits_collected() >= 128)
+ /*
+ Consider ourselves seeded once we've collected an estimated 128 bits of
+ entropy in a single poll.
+ */
+ if(seeded == false && accum.bits_collected() >= 128)
seeded = true;
}
@@ -119,15 +123,18 @@ void HMAC_RNG::reseed(size_t poll_bits)
*/
void HMAC_RNG::add_entropy(const byte input[], size_t length)
{
+ const size_t USER_ENTROPY_WATERSHED = 20;
+
extractor->update(input, length);
user_input_len += length;
/*
- * After we've accumulated >= 1024 bytes of user input, reseed.
- * This input will automatically have been included if reseed was
- * called already, as it's just included in the extractor input.
+ * After we've accumulated at least USER_ENTROPY_WATERSHED bytes of
+ * user input, reseed. This input will automatically have been
+ * included if reseed was called already, as it's just included in
+ * the extractor input.
*/
- if(user_input_len >= 1024)
+ if(user_input_len >= USER_ENTROPY_WATERSHED)
reseed(128);
}