ThreadedRSAKey.java\u00a0 Illustrates converting a method in an existing class from a single-threaded method to a multi-threaded method. In this example, RSAKey\u00a0 computes an RSA public-private key pair, where the key size has a specified number of digits. As large prime numbers require considerable CPU time, ThreadedRSAKey converts the original computeKey method in RSAKey\u00a0 to a multi-threaded method, thus allowing simultaneous (multithreaded) computation of multiple key pairs. Uses the following classes:<\/p>\n
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import java.io.*;\u00a0 \u00a0\r\n\r\n\u00a0* RSAKey.java Computes RSA public-private key pairs of arbitrary length.\r\n\r\n\r\n\u00a0* Primes.java Generates large prime numbers.\r\n\r\n\r\n\/** An example of creating a background process for an\r\n\u00a0*\u00a0 originally nonthreaded, class method. Normally,\r\n\u00a0*\u00a0 the program flow will wait until computeKey is finished.\r\n\u00a0\r\npublic class ThreadedRSAKey extends RSAKey implements Runnable {\r\n\r\n\u00a0 \/\/ Store strNumDigits into the thread to prevent race\r\n\u00a0 \/\/ conditions.\r\n\u00a0 public void computeKey(String strNumDigits) {\r\n\u00a0\u00a0\u00a0 RSAThread t = new RSAThread(this, strNumDigits);\r\n\u00a0\u00a0\u00a0 t.start();\r\n\u00a0 }\r\n\r\n\u00a0 \/\/ Retrieve the stored strNumDigits and call the original\r\n\u00a0 \/\/ method.\u00a0 Processing is now done in the background.\r\n\u00a0 public void run() {\r\n\u00a0\u00a0\u00a0 RSAThread t = (RSAThread)Thread.currentThread();\r\n\u00a0\u00a0\u00a0 String strNumDigits = t.getStrDigits();\r\n\u00a0\u00a0\u00a0 super.computeKey(strNumDigits);\r\n\u00a0 }\r\n\r\n\u00a0 public static void main(String[] args){\r\n\u00a0\u00a0\u00a0 ThreadedRSAKey key = new ThreadedRSAKey();\r\n\u00a0\u00a0\u00a0 for (int i=0; i \" + n);\r\n\u00a0\u00a0\u00a0 System.out.println(\"public\u00a0 => \" + encrypt);\r\n\u00a0\u00a0\u00a0 System.out.println(\"private => \" + decrypt);\r\n\u00a0 }\r\n}\r\n\r\n\r\n\u00a0* Primes.java Generates large prime numbers.\r\n***\r\n\r\nimport java.math.BigInteger;\r\n\r\n\/** A few utilities to generate a large random BigInteger,\r\n\u00a0*\u00a0 and find the next prime number above a given BigInteger.\r\n\u00a0\r\npublic class Primes {\r\n\u00a0 \/\/ Note that BigInteger.ZERO was new in JDK 1.2, and 1.1\r\n\u00a0 \/\/ code is being used to support the most servlet engines.\r\n\u00a0 private static final BigInteger ZERO = new BigInteger(\"0\");\r\n\u00a0 private static final BigInteger ONE = new BigInteger(\"1\");\r\n\u00a0 private static final BigInteger TWO = new BigInteger(\"2\");\r\n\u00a0 \r\n\u00a0 \/\/ Likelihood of false prime is less than 1\/2^ERR_VAL\r\n\u00a0 \/\/ Assumedly BigInteger uses the Miller-Rabin test or\r\n\u00a0 \/\/ equivalent, and thus is NOT fooled by Carmichael numbers.\r\n\u00a0 \/\/ See section 33.8 of Cormen et al. Introduction to\r\n\u00a0 \/\/ Algorithms for details.\r\n\u00a0 private static final int ERR_VAL = 100;\r\n\u00a0 \r\n\u00a0 public static BigInteger nextPrime(BigInteger start) {\r\n\u00a0\u00a0\u00a0 if (isEven(start))\r\n\u00a0\u00a0\u00a0\u00a0\u00a0 start = start.add(ONE);\r\n\u00a0\u00a0\u00a0 else\r\n\u00a0\u00a0\u00a0\u00a0\u00a0 start = start.add(TWO);\r\n\u00a0\u00a0\u00a0 if (start.isProbablePrime(ERR_VAL))\r\n\u00a0\u00a0\u00a0\u00a0\u00a0 return(start);\r\n\u00a0\u00a0\u00a0 else\r\n\u00a0\u00a0\u00a0\u00a0\u00a0 return(nextPrime(start));\r\n\u00a0 }\r\n\r\n\u00a0 private static boolean isEven(BigInteger n) {\r\n\u00a0\u00a0\u00a0 return(n.mod(TWO).equals(ZERO));\r\n\u00a0 }\r\n\r\n\u00a0 private static StringBuffer[] digits =\r\n\u00a0\u00a0\u00a0 { new StringBuffer(\"0\"), new StringBuffer(\"1\"),\r\n\u00a0\u00a0\u00a0\u00a0\u00a0 new StringBuffer(\"2\"), new StringBuffer(\"3\"),\r\n\u00a0\u00a0\u00a0\u00a0\u00a0 new StringBuffer(\"4\"), new StringBuffer(\"5\"),\r\n\u00a0\u00a0\u00a0\u00a0\u00a0 new StringBuffer(\"6\"), new StringBuffer(\"7\"),\r\n\u00a0\u00a0\u00a0\u00a0\u00a0 new StringBuffer(\"8\"), new StringBuffer(\"9\") };\r\n\r\n\u00a0 private static StringBuffer randomDigit() {\r\n\u00a0\u00a0\u00a0 int index = (int)Math.floor(Math.random() * 10);\r\n\u00a0\u00a0\u00a0 return(digits[index]);\r\n\u00a0 }\r\n\u00a0 \r\n\u00a0 public static BigInteger random(int numDigits) {\r\n\u00a0\u00a0\u00a0 StringBuffer s = new StringBuffer(\"\");\r\n\u00a0\u00a0\u00a0 for(int i=0; i 0)\r\n\u00a0\u00a0\u00a0\u00a0\u00a0 numDigits = Integer.parseInt(args[0]);\r\n\u00a0\u00a0\u00a0 else\r\n\u00a0\u00a0\u00a0\u00a0\u00a0 numDigits = 150;\r\n\u00a0\u00a0\u00a0 BigInteger start = random(numDigits);\r\n\u00a0\u00a0\u00a0 for(int i=0; i<50; i++) {\r\n\u00a0\u00a0\u00a0\u00a0\u00a0 start = nextPrime(start);\r\n\u00a0\u00a0\u00a0\u00a0\u00a0 System.out.println(\"Prime \" + i + \" = \" + start);\r\n\u00a0\u00a0\u00a0 }\r\n\u00a0 }\r\n}<\/pre>\n","protected":false},"excerpt":{"rendered":"ThreadedRSAKey.java\u00a0 Illustrates converting a method in an existing class from a single-threaded method to a multi-threaded method. In this example, RSAKey\u00a0 computes an RSA public-private key pair, where the key size has a specified number of digits. As large prime numbers require considerable CPU time, ThreadedRSAKey converts the original computeKey method in RSAKey\u00a0 to a … <\/p>\n