Java Security

Last edited: 2 Oct 2019

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JCE - Encryption - Message Digests

Q: Using JCE I am getting a BadPaddingException?. What should I do?

A: Search the forums for "BadPaddingException?" for several discussions on this. The gist is: don't use a String to store the encrypted text - use byte[].

Q: Where can I get Java source code for the XYZ algorithm?

A: Bouncycastle is an open source library comprised of many and varied encryption algorithms, amongst them a full JCE implementation. The codes for the AES competition are also available. Those include Rijndael (which became AES), RC6, Serpent, Twofish and Mars.

Q: I am getting an java.lang.SecurityException?: Unsupported keysize or algorithm parameters. What gives?

A: One reason may be that you're using incorrect parameters for the algorithm, mode or cipher. Check the above-mentioned list of algorithms for what is available. Another reason may be that you don't have the unlimited jurisdiction policy files installed; these can be downloaded from the same place you download the J2SE JDK.

Q: How can I implement my own JCE provider?

A: This is described in detail in the article How To Implement a Provider for the Java Cryptography Architecture. Information on how to install the provider can be found in the sections on "How Provider Implementations Are Requested and Supplied" and "Installing Providers" in this article.

Q: Which message digest (or hash) algorithm should I use?

A: At this point, the various RC, MD and SHA-1 algorithms should no longer be used. SHA-2 is the way to go; it's available in Java in the SHA-256, SHA-384 and SHA-512 variants. (A NIST competition has selected a SHA-3 standard, but it's not yet part of the JRE, and anyway offers no fundamental advantage over SHA-2.)


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