1 files changed, 12 insertions, 4 deletions
diff --git a/crypto/src/crypto/generators/SCrypt.cs b/crypto/src/crypto/generators/SCrypt.cs
index 64a36df63..4d15bb3d7 100644
--- a/crypto/src/crypto/generators/SCrypt.cs
+++ b/crypto/src/crypto/generators/SCrypt.cs
@@ -1,5 +1,5 @@
using System;
-using System.Threading;
+using System.Diagnostics;
using Org.BouncyCastle.Crypto.Digests;
using Org.BouncyCastle.Crypto.Engines;
@@ -31,8 +31,8 @@ namespace Org.BouncyCastle.Crypto.Generators
throw new ArgumentNullException("Passphrase P must be provided.");
if (S == null)
throw new ArgumentNullException("Salt S must be provided.");
- if (N <= 1)
- throw new ArgumentException("Cost parameter N must be > 1.");
+ if (N <= 1 || !IsPowerOf2(N))
+ throw new ArgumentException("Cost parameter N must be > 1 and a power of 2.");
// Only value of r that cost (as an int) could be exceeded for is 1
if (r == 1 && N >= 65536)
throw new ArgumentException("Cost parameter N must be > 1 and < 65536.");
@@ -170,5 +170,13 @@ namespace Org.BouncyCastle.Crypto.Generators
Clear(array);
}
}
- }
+
+ // note: we know X is non-zero
+ private static bool IsPowerOf2(int x)
+ {
+ Debug.Assert(x != 0);
+
+ return (x & (x - 1)) == 0;
+ }
+ }
}
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