diff options
author | David Hook <dgh@cryptoworkshop.com> | 2013-05-31 11:07:45 +0400 |
---|---|---|
committer | David Hook <dgh@cryptoworkshop.com> | 2013-05-31 11:07:45 +0400 |
commit | 2b976f5364cfdbc37d3086019d93483c983eb80b (patch) | |
tree | cb846af3fd1d43f9c2562a1fb2d06b997ad8f229 /core/src/main/java/org/bouncycastle/crypto/prng/ReversedWindowGenerator.java | |
parent | 5f714bd92fbd780d22406f4bc3681be005f6f04a (diff) |
initial reshuffle
Diffstat (limited to 'core/src/main/java/org/bouncycastle/crypto/prng/ReversedWindowGenerator.java')
-rw-r--r-- | core/src/main/java/org/bouncycastle/crypto/prng/ReversedWindowGenerator.java | 111 |
1 files changed, 111 insertions, 0 deletions
diff --git a/core/src/main/java/org/bouncycastle/crypto/prng/ReversedWindowGenerator.java b/core/src/main/java/org/bouncycastle/crypto/prng/ReversedWindowGenerator.java new file mode 100644 index 00000000..fbb2639c --- /dev/null +++ b/core/src/main/java/org/bouncycastle/crypto/prng/ReversedWindowGenerator.java @@ -0,0 +1,111 @@ +package org.bouncycastle.crypto.prng; + +/** + * Takes bytes generated by an underling RandomGenerator and reverses the order in + * each small window (of configurable size). + * <p> + * Access to internals is synchronized so a single one of these can be shared. + * </p> + */ +public class ReversedWindowGenerator + implements RandomGenerator +{ + private final RandomGenerator generator; + + private byte[] window; + private int windowCount; + + public ReversedWindowGenerator( + RandomGenerator generator, + int windowSize) + { + if (generator == null) + { + throw new IllegalArgumentException("generator cannot be null"); + } + if (windowSize < 2) + { + throw new IllegalArgumentException("windowSize must be at least 2"); + } + + this.generator = generator; + this.window = new byte[windowSize]; + } + + /** + * Add more seed material to the generator. + * + * @param seed a byte array to be mixed into the generator's state. + */ + public void addSeedMaterial( + byte[] seed) + { + synchronized (this) + { + windowCount = 0; + generator.addSeedMaterial(seed); + } + } + + /** + * Add more seed material to the generator. + * + * @param seed a long value to be mixed into the generator's state. + */ + public void addSeedMaterial( + long seed) + { + synchronized (this) + { + windowCount = 0; + generator.addSeedMaterial(seed); + } + } + + /** + * Fill bytes with random values. + * + * @param bytes byte array to be filled. + */ + public void nextBytes( + byte[] bytes) + { + doNextBytes(bytes, 0, bytes.length); + } + + /** + * Fill part of bytes with random values. + * + * @param bytes byte array to be filled. + * @param start index to start filling at. + * @param len length of segment to fill. + */ + public void nextBytes( + byte[] bytes, + int start, + int len) + { + doNextBytes(bytes, start, len); + } + + private void doNextBytes( + byte[] bytes, + int start, + int len) + { + synchronized (this) + { + int done = 0; + while (done < len) + { + if (windowCount < 1) + { + generator.nextBytes(window, 0, window.length); + windowCount = window.length; + } + + bytes[start + done++] = window[--windowCount]; + } + } + } +} |