KeyGenerator

public class KeyGenerator
extends Object

java.lang.Object
   ↳ javax.crypto.KeyGenerator

This class provides the functionality of a secret (symmetric) key generator.

Key generators are constructed using one of the getInstance class methods of this class.

KeyGenerator objects are reusable, i.e., after a key has been generated, the same KeyGenerator object can be re-used to generate further keys.

There are two ways to generate a key: in an algorithm-independent manner, and in an algorithm-specific manner. The only difference between the two is the initialization of the object:

  • Algorithm-Independent Initialization

    All key generators share the concepts of a keysize and a source of randomness. There is an init method in this KeyGenerator class that takes these two universally shared types of arguments. There is also one that takes just a keysize argument, and uses the SecureRandom implementation of the highest-priority installed provider as the source of randomness (or a system-provided source of randomness if none of the installed providers supply a SecureRandom implementation), and one that takes just a source of randomness.

    Since no other parameters are specified when you call the above algorithm-independent init methods, it is up to the provider what to do about the algorithm-specific parameters (if any) to be associated with each of the keys.

  • Algorithm-Specific Initialization

    For situations where a set of algorithm-specific parameters already exists, there are two init methods that have an AlgorithmParameterSpec argument. One also has a SecureRandom argument, while the other uses the SecureRandom implementation of the highest-priority installed provider as the source of randomness (or a system-provided source of randomness if none of the installed providers supply a SecureRandom implementation).

In case the client does not explicitly initialize the KeyGenerator (via a call to an init method), each provider must supply (and document) a default initialization.

Android provides the following KeyGenerator algorithms:

Algorithm Supported API Levels
AES 1+
AESWRAP 1-8
ARC4 14+
BLOWFISH 10+
ChaCha20 28+
DES 1+
DESede 1+
DESedeWRAP 1-8
HmacMD5 1+
HmacSHA1 11+
HmacSHA224 1-8,22+
HmacSHA256 1+
HmacSHA384 1+
HmacSHA512 1+
RC4 10-13
These algorithms are described in the KeyGenerator section of the Java Cryptography Architecture Standard Algorithm Name Documentation.

See also:

Summary