Converting Secret Keys to and from Byte Arrays

This section provides a quick introduction of the SecretKeySpec class and the KeySpec interface. They can be used to convert secret keys into byte arrays to store them in external files.

Converting a secret key to a byte array is supported by the SecretKey interface with the getEncoded() method. All secret key implementation classes use the RAW encoding format.

Converting a secret key from a byte array is not so easy. Two options are available:

1. javax.crypto.spec.SecretKeySpec is a class represents a secret key in a generic fashion. It offers the following constructor and methods:

SecretKeySpec() - Convert a secret key from the specified byte array according to the specified algorithm and constructs a SecretKeySpec object based on the secret key.

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.

2. is an interface providing a grouping point for algorithm specific key specification implementations. There are two implementations for secret key algorithms:

javax.crypto.spec.DESKeySpec is a KeySpec implementation for DES algorithm. It offers DESKeySpec() to construct a KeySpec object from the specific byte array.

javax.crypto.spec.DESedeKeySpec is a KeySpec implementation for DESede algorithm. It offers DESedeKeySpec() to construct a KeySpec object from the specific byte array.

javax.crypto.spec.SecretKeyFactory is a class as a conversion tool between SecretKey objects and algorithm specific KeySpec objects. It offers the following methods:

getInstance() - Returns a SecretKeyFactory object of the specified algorithm and the specified security package provider. If not specified, the default security package provider will be used.

generateSecret() - Generates a SecretKey object from the specified KeySpec object, and returns it.

getKeySpec() - Converts a SecretKey object to a KeySpec object, and returns it.

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

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

See the next section on how to use the SecretKeySpec class and the KeySpec interface in a sample program.

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 About This JDK Tutorial Book

 JDK (Java Development Kit)

 Java Date-Time API

 Date, Time and Calendar Classes

 Date and Time Object and String Conversion

 Number Object and Numeric String Conversion

 Locales, Localization Methods and Resource Bundles

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 Message Digest Algorithm Implementations in JDK

 Private key and Public Key Pair Generation

 PKCS#8/X.509 Private/Public Encoding Standards

 Digital Signature Algorithm and Sample Program

 "keytool" Commands and "keystore" Files

 KeyStore and Certificate Classes

Secret Key Generation and Management

 javax.crypto.SecretKey - The Secret Key Interface

 javax.crypto.KeyGenerator - Generating Secret Keys

Converting Secret Keys to and from Byte Arrays - Secret Key Test Program

 Cipher - Encryption and Decryption

 The SSL (Secure Socket Layer) Protocol

 SSL Socket Communication Testing Programs

 SSL Client Authentication

 HTTPS (Hypertext Transfer Protocol Secure)

 Outdated Tutorials


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