Skip to content

Instantly share code, notes, and snippets.

Created August 22, 2022 08:59
Show Gist options
  • Save jiacheo/c01ca88ee308a8fe8293452cc71fdcb5 to your computer and use it in GitHub Desktop.
Save jiacheo/c01ca88ee308a8fe8293452cc71fdcb5 to your computer and use it in GitHub Desktop.
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="" target="_blank">jiacheo[at]</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));
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
Copy link

jiacheo commented Aug 22, 2022

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

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment