Cryptography Tutorials - Herong's Tutorial Examples

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

∟java.security.KeyFactory - Reading Encoded Keys

This section describes the java.security.KeyFactory class, which allows you to convert key spec objects back to key objects. Full process of reading and converting encoded key files back to key objects are also provided.

In the previous chapter, we learned how to write keys into files as encoded byte strings generated by the java.security.Key.getEncoded() method. Now we want to learn how to read those encoded type strings back and convert them into keys using 3 classes: java.security.spec.PKCS8EncodedKeySpec, java.security.spec.X509EncodedKeySpec, and java.security.KeyFactory.

PKCS8EncodedKeySpec and X509EncodedKeySpec classes are described in the previous section. Here is a quick description of the KeyFactory class.

java.security.KeyFactory - A class to convert keys between Key objects and EncodedKeySpec objects. Major methods offered:

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

generatePrivate() - Generates a PrivateKey object based on the specified EncodedKeySpec object, and returns it.

generatePublic() - Generates a PublicKey object based on the specified EncodedKeySpec object, and returns it.

getKeySpec() - Converts a Key object to an EncodedKeySpec object, and returns it.

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

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

To read an encoded byte string and convert it back a key, you need to follow these steps:

• Read the encoded byte string from a file into a byte array.
• Convert the byte array into a key spec object using the PKCS8EncodedKeySpec or X509EncodedKeySpec constructor.
• Then convert the key spec object into a key object using the generatePrivate() or generatePublic() of a KeyFactory object of the correct encryption algorithm.

See the next section on how to write a sample program.

Table of Contents

 About This Book

 Cryptography Terminology

 Cryptography Basic Concepts

 Introduction to AES (Advanced Encryption Standard)

 Introduction to DES Algorithm

 DES Algorithm - Illustrated with Java Programs

 DES Algorithm Java Implementation

 DES Algorithm - Java Implementation in JDK JCE

 DES Encryption Operation Modes

 DES in Stream Cipher Modes

 PHP Implementation of DES - mcrypt

 Blowfish - 8-Byte Block Cipher

 Secret Key Generation and Management

 Cipher - Secret Key Encryption and Decryption

 Introduction of RSA Algorithm

 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

 What Is Key Encoding?

 PKCS#8 and X.509 Key Encoding Classes

►java.security.KeyFactory - Reading Encoded Keys

 JcaKeyFactoryTest.java - Key Factory Test Program

 Reading DSA Private and Public Key Files

 Reading RSA Private and Public Key Files

 Cipher - Public Key Encryption and Decryption

 MD5 Mesasge Digest Algorithm

 SHA1 Mesasge Digest Algorithm

 OpenSSL Introduction and Installation

 OpenSSL Generating and Managing RSA Keys

 OpenSSL Managing Certificates

 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"

 Using Certificates in IE

 Using Certificates in Google Chrome

 Using Certificates in Firefox

 Archived Tutorials

 References

 Full Version in PDF/EPUB

java.security.KeyFactory - Reading Encoded Keys - Updated in 2023, by Herong Yang