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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.security;
import org.bouncycastle.util.Arrays;
/**
* Utility functions for comparing the contents of arrays without leaking information about the
* data contained within them via timing side-channels. This is done by avoiding any branches
* that depend on the array elements themselves. This inherently means that all operations have
* both an upper and a lower bound in processing time that is O(n) for an array of size n, as there
* can be no early exits.
*
* @author vekterli
*/
public class SideChannelSafe {
/**
* @return true iff all bytes in the array are zero. An empty array always returns true
* to be in line with BouncyCastle semantics.
*/
public static boolean allZeros(byte[] buf) {
return Arrays.areAllZeroes(buf, 0, buf.length);
}
/**
* Compare two byte arrays without the use of data-dependent branching that may leak information
* about the contents of either of the arrays.
*
* <strong>Important:</strong> the <em>length</em> of the arrays is not considered secret, and
* <em>may</em> be leaked if arrays of differing sizes are given.
*
* @param lhs first array of bytes to compare
* @param rhs second array of bytes to compare
* @return true iff both arrays have the same size and are element-wise identical
*/
public static boolean arraysEqual(byte[] lhs, byte[] rhs) {
return Arrays.constantTimeAreEqual(lhs, rhs);
}
}
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