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Increase number of attempts before failure in ECDSA-DER #33933

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merged 2 commits into from
Mar 22, 2020
Merged

Increase number of attempts before failure in ECDSA-DER #33933

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823d2c8
Increase number of attempts before failure in ECDSA-DER
bartonjs Mar 22, 2020
6cb95fb
Billion, with a b.
bartonjs Mar 22, 2020
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12 changes: 8 additions & 4 deletions .../System/Security/Cryptography/AlgorithmImplementations/ECDsa/ECDsaSignatureFormatTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -331,15 +331,17 @@ public void Rfc23279TrySignHashUnderMax()
ECDsa key = (ECDsa)keyDescription.Key;

const DSASignatureFormat SignatureFormat = DSASignatureFormat.Rfc3279DerSequence;
const int RetryCount = 10;
// Make secp521r1 (7/16 chance of being smaller) and mod-8 keys (3/4 chance of being smaller)
// have the same 1-in-a-billion chance of failure.
int retryCount = keyDescription.FieldSizeInBits % 8 == 1 ? 36 : 15;
byte[] hash = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 };

int expectedSize = GetExpectedSize(keyDescription.FieldSizeInBits);
int maxSize = key.GetMaxSignatureSize(DSASignatureFormat.Rfc3279DerSequence);
Assert.True(expectedSize < maxSize, "expectedSize < maxSize");
byte[] signature = new byte[expectedSize];

for (int i = 0; i < RetryCount; i++)
for (int i = 0; i < retryCount; i++)
{
if (key.TrySignHash(hash, signature, SignatureFormat, out int written))
{
Expand All @@ -359,15 +361,17 @@ public void Rfc23279TrySignDataUnderMax()
ECDsa key = (ECDsa)keyDescription.Key;

const DSASignatureFormat SignatureFormat = DSASignatureFormat.Rfc3279DerSequence;
const int RetryCount = 10;
// Make secp521r1 (7/16 chance of being smaller) and mod-8 keys (3/4 chance of being smaller)
// have the same 1-in-a-billion chance of failure.
int retryCount = keyDescription.FieldSizeInBits % 8 == 1 ? 36 : 15;
HashAlgorithmName hashAlgorithm = HashAlgorithmName.SHA1;

int expectedSize = GetExpectedSize(keyDescription.FieldSizeInBits);
int maxSize = key.GetMaxSignatureSize(DSASignatureFormat.Rfc3279DerSequence);
Assert.True(expectedSize < maxSize, "expectedSize < maxSize");
byte[] signature = new byte[expectedSize];

for (int i = 0; i < RetryCount; i++)
for (int i = 0; i < retryCount; i++)
{
if (key.TrySignData(Array.Empty<byte>(), signature, hashAlgorithm, SignatureFormat, out int written))
{
Expand Down