1 package com.brian_web.crypto;
3 import java.security.SecureRandom;
7 private final SecureRandom srand;
8 public PKCS1(RSA rsa) { this(rsa,new SecureRandom()); }
9 public PKCS1(RSA rsa,SecureRandom srand) { this.rsa = rsa; this.srand = srand; }
11 public byte[] encode(byte[] in) {
12 int size = rsa.getInputBlockSize();
13 if(in.length > size - 11) throw new IllegalArgumentException("message too long");
14 byte[] buf = new byte[size];
15 byte[] rand = new byte[size - in.length - 2];
16 srand.nextBytes(rand);
17 for(int i=0;i<rand.length;i++) while(rand[i] == 0) rand[i] = (byte)srand.nextInt();
20 System.arraycopy(rand,0,buf,p,rand.length);
23 System.arraycopy(in,0,buf,p,in.length);
25 return rsa.process(buf);
28 public byte[] decode(byte[] in) throws Exn {
29 byte[] buf = rsa.process(in);
30 if(buf.length < 10) throw new Exn("Data too short");
31 if(buf[0] != 2 && buf[0] != 1) throw new Exn("Data not in correct format " + (buf[0]&0xff));
33 while(start < buf.length && buf[start] != 0) start++;
34 if(start == buf.length) throw new Exn("No null separator");
36 byte[] ret = new byte[buf.length - start];
37 System.arraycopy(buf,start,ret,0,ret.length);
41 public static class Exn extends Exception { public Exn(String s) { super(s); } }