JCE - Cipher - Encryption and Decryption

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This chapter describes some parts of the JCE (Java Cryptography Extension) which has been introduced in JDK since 1.1:

• What is a secret key?
• Classes in JDK to generate a secret key.
• Classes in JDK to write and read a secret key to and from a file.
• A sample program to generate, write, and read a secret key.

What Is a Secret Key?

A secrete key is the key used in a symmetric encryption algorithm, where the same key is used both the encryption process and the decryption process.

Known symmetric encryption algorithms:

• Blowfish - The block cipher designed by Bruce Schneier.
• DES - The Digital Encryption Standard as described in FIPS PUB 46-2.
• DESede - Triple DES Encryption (DES-EDE).

The SecretKey Interface

javax.crypto.SecretKey is an interface providing a grouping point for various secret keys. It extents java.security.Key, and inherits 3 methods:

getAlgorithm() - Returns the algorithm name used to generate the key.

getEncoded() - Returns the key as a byte array in its primary encoding format.

getFormat() - Returns the name of the primary encoding format of this key.

The KeyGenerator Class

javax.crypto.KeyGenerator is an abstract class providing a link to implementation classes of secret key generration algorithms provided by various security package providers. Major methods in the KeyGenerator class:

getInstance() - Returns a KeyGenerator object of the specified algorithm from the implementation of the specified provider. If provider is not specified, the default implementation is used. This is a static method.

init() - Initializes this key generator with the specified key size.

generateKey() - Generates a key and returns it as a SecretKey object.

getAlgorithm() - Returns the algorithm name of this generator.

getProvider() - Returns the provider as a Provider object of this generator.

(Continued on next part...)

Part:   1   2  3