Cryptography Tutorials - Herong's Tutorial Examples - Version 5.36, by Dr. Herong Yang
RsaKeyGenerator.java for RSA Key Generation
This section describes the initial draft of a RSA public key and private key generation implementation using the java.math.BigInteger class.
The first step of RSA public key encryption implementation is to write a program to generate a pair of public key and private key. Here is my initial draft using the java.math.BigInteger class:
/* RsaKeyGenerator.java #- Copyright (c) 2013, HerongYang.com, All Rights Reserved. */ import java.math.BigInteger; import java.util.Random; class RsaKeyGenerator { public static void main(String[] a) { if (a.length<1) { System.out.println("Usage:"); System.out.println("java RsaKeyGenerator size"); return; } int size = Integer.parseInt(a[0]); Random rnd = new Random(); BigInteger p = BigInteger.probablePrime(size/2,rnd); BigInteger q = p.nextProbablePrime(); BigInteger n = p.multiply(q); BigInteger m = (p.subtract(BigInteger.ONE)).multiply( q.subtract(BigInteger.ONE)); BigInteger e = getCoprime(m); BigInteger d = e.modInverse(m); System.out.println("p: "+p); System.out.println("q: "+q); System.out.println("m: "+m); System.out.println("Modulus: "+n); System.out.println("Key size: "+n.bitLength()); System.out.println("Public key: "+e); System.out.println("Private key: "+d); } public static BigInteger getCoprime(BigInteger m) { Random rnd = new Random(); int length = m.bitLength()-1; BigInteger e = BigInteger.probablePrime(length,rnd); while (! (m.gcd(e)).equals(BigInteger.ONE) ) { e = BigInteger.probablePrime(length,rnd); } return e; } }
Some notes on RsaKeyGenerator.java:
See the next tutorial for testing result of this program.
Last update: 2013.
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
Generating Prime Number with BigInteger Class
Performance of Prime Number Generation
RSA Encryption Implementation using BigInteger Class
►RsaKeyGenerator.java for RSA Key Generation
RSA Keys Generated by RsaKeyGenerator.java
RsaKeyValidator.java for RSA Key Validation
64-bit RSA Key Validated by RsaKeyValidator.java
Converting Byte Sequences to Positive Integers
Cleartext Block Size for RSA Encryption
Cleartext Message Padding and Revised Block Size
Ciphertext Block Size for RSA Encryption
RsaKeyEncryption.java for RSA Encryption Operation
RsaKeyDecryption.java for RSA Decryption Operation
Testing RsaKeyEncryption.java with a 16-bit Key
Testing RsaKeyEncryption.java with a 64-bit Key
Testing RsaKeyEncryption.java with a 3072-bit Key
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
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"
Using Certificates in IE (Internet Explorer)