**Cryptography Tutorials - Herong's Tutorial Examples** - v5.40, by Dr. Herong Yang

javax.crypto.Cipher - The Public Key Encryption Class

This section provides a quick introduction of the cipher class, javax.crypto.Cipher, to encrypt input data with a public key.

In the previous chapter, I learned how to use classes and interfaces in the JCE (Java Cryptography Extension) package to generate and manage private and public keys. Now I am ready to learn how to use private keys to encrypt or cipher any input data using the javax.crypto.Cipher class.

javax.crypto.Cipher is a class that provides functionality of a cryptographic cipher for encryption and decryption. It has the following major methods.

getInstance() - Returns a Cipher object of the specified transformation (algorithm plus options) 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 cipher for the specified operation mode with the specified key or public key certificate. Two important operation modes are Cipher.ENCRYPT_MODE and Cipher.DECRYPT_MODE.

update() - Feeds additional input data to this cipher and generates partial output data.

doFinal() - Feeds the last part of the input data to this cipher and generates the last part of the output data.

getBlockSize() - Returns the block size of this cipher.

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

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

See the next section how to use the javax.crypto.Cipher class in a sample program.

Table of Contents

Introduction to AES (Advanced Encryption Standard)

DES Algorithm - Illustrated with Java Programs

DES Algorithm Java Implementation

DES Algorithm - Java Implementation in JDK JCE

DES Encryption Operation Modes

PHP Implementation of DES - mcrypt

Blowfish - 8-Byte Block Cipher

Secret Key Generation and Management

Cipher - Secret Key Encryption and Decryption

RSA Implementation using java.math.BigInteger Class

Introduction of DSA (Digital Signature Algorithm)

Java Default Implementation of DSA

Private key and Public Key Pair Generation

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

►Cipher - Public Key Encryption and Decryption

►javax.crypto.Cipher - The Public Key Encryption Class

JcePublicCipher.java - Public Key Encryption Sample Program

DSA Public Key Encryption Tests

RSA Public Key Encryption Tests

OpenSSL Introduction and Installation

OpenSSL Generating and Managing RSA Keys

OpenSSL Generating and Signing CSR

OpenSSL Validating Certificate Path

"keytool" and "keystore" from JDK

"OpenSSL" Signing CSR Generated by "keytool"

Migrating Keys from "keystore" to "OpenSSL" Key Files

Certificate X.509 Standard and DER/PEM Formats

Migrating Keys from "OpenSSL" Key Files to "keystore"