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@jiacheo
Created August 22, 2022 08:59
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simple rsa demo
package org.jiacheo.awesome.blockchain.encrypt.communication;
import java.math.BigInteger;
import java.util.Random;
/**
* Created on 2022/8/22. <br/> contact: <a style="color:yellow;text-decoration:none;"
* href="mailto:jiacheo@qipeng.com" target="_blank">jiacheo[at]qipeng.com</a> <br/>
*
* @author jiacheo
*/
public class SimpleRSA {
public static void main(String[] args) {
BigInteger ONE = new BigInteger("1");
BigInteger TWO = new BigInteger("2");
//random p、q,created for generate n、d、e,than drop them。
BigInteger p = new BigInteger(128, 128, new Random());
BigInteger q = new BigInteger(128, 128, new Random());
BigInteger n = q.multiply(p);
BigInteger upperLimit = n.subtract(ONE);
//选择从1到n-1之间的一个随机数,且该随机数不能是偶数。否则BigInteger.modInverse 会抛异常
BigInteger d;
Random random = new Random();
do {
d = new BigInteger(upperLimit.bitLength(), random);
}
while (d.compareTo(upperLimit) >= 0 || d.compareTo(ONE) <= 0 || d.mod(TWO).compareTo(ONE) < 0);
System.out.println("p=0x" + p.toString(16));
System.out.println("q=0x" + q.toString(16));
System.out.println("n=0x" + n.toString(16));
System.out.println("d=0x" + d.toString(16));
BigInteger modulo = p.subtract(ONE).multiply(q.subtract(ONE));
System.out.println("m=0x"+modulo.toString(16));
BigInteger e = d.modInverse(modulo);
System.out.println("e=0x" + e.toString(16));
//source data
BigInteger sourceMessage = BigInteger.probablePrime(128, random);
System.out.println("sourceMessage=" + sourceMessage.toString(36));
//encrypt, e/n pair is public key
BigInteger data = sourceMessage.modPow(e, n);
System.out.println("encryptedData=0x" + data.toString(16));
//decrypt, d/n pair is private key
BigInteger decryptedData = data.modPow(d, n);
System.out.println("decryptedData=" + decryptedData.toString(36));
//compare equivalent
System.out.println("equals?="+sourceMessage.equals(decryptedData));
}
}
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jiacheo commented Aug 22, 2022

come from the paper (author by Christian Reitwießner), the theory shows as below screent shots:
image

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