1 package org.bouncycastle.crypto.paddings; 2 3 import java.security.SecureRandom; 4 5 import org.bouncycastle.crypto.InvalidCipherTextException; 6 7 /** 8 * A padder that adds the padding according to the scheme referenced in 9 * ISO 7814-4 - scheme 2 from ISO 9797-1. The first byte is 0x80, rest is 0x00 10 */ 11 public class ISO7816d4Padding 12 implements BlockCipherPadding 13 { 14 /** 15 * Initialise the padder. 16 * 17 * @param random - a SecureRandom if available. 18 */ 19 public void init(SecureRandom random) 20 throws IllegalArgumentException 21 { 22 // nothing to do. 23 } 24 25 /** 26 * Return the name of the algorithm the padder implements. 27 * 28 * @return the name of the algorithm the padder implements. 29 */ 30 public String getPaddingName() 31 { 32 return "ISO7816-4"; 33 } 34 35 /** 36 * add the pad bytes to the passed in block, returning the 37 * number of bytes added. 38 */ 39 public int addPadding( 40 byte[] in, 41 int inOff) 42 { 43 int added = (in.length - inOff); 44 45 in [inOff]= (byte) 0x80; 46 inOff ++; 47 48 while (inOff < in.length) 49 { 50 in[inOff] = (byte) 0; 51 inOff++; 52 } 53 54 return added; 55 } 56 57 /** 58 * return the number of pad bytes present in the block. 59 */ 60 public int padCount(byte[] in) 61 throws InvalidCipherTextException 62 { 63 int count = in.length - 1; 64 65 while (count > 0 && in[count] == 0) 66 { 67 count--; 68 } 69 70 if (in[count] != (byte)0x80) 71 { 72 throw new InvalidCipherTextException("pad block corrupted"); 73 } 74 75 return in.length - count; 76 } 77 } 78
