conversion.java

身份认证和数字签名在实际应用中是通过以数字证书为核心的公开密钥基础结构(PKI)来实现的

/****************************************************************
* 软件:Java签名协议扩展 (Java Signature Protocol Extension, JSPE)
* 版本:V1.0
* 软件功能:实现SSL签名协议
* 模块:公共类Conversion
*-----------------------------------------------------------------
*  本模块来自文献[19]:Jamie Jaworski.Java Security Handbook.邱仲潘译.电子工业出版社.2001年
*                        版权归Jamie Jaworski所有
******************************************************************/
package com.zsusoft.zfl;
import java.util.*;
// Provides static type/format conversion methods.
/*****************************************************************************************
*  数组和字符串之间的转换工具(Jamie Jaworski提供).
******************************************************************************************/
public class Conversion {
 private static String[] hexDigits = {"0","1","2","3","4","5","6","7",
   "8","9","a","b","c","d","e","f"};
 /**
 * Convert a byte to a hexadecimal String
 **/
 public static String byteToHexString(byte b) {
  int n = b;
  if(n < 0) n = 256 + n;
  int d1 = n / 16;
  int d2 = n % 16; 
  return hexDigits[d1]+hexDigits[d2];
 }
 /**
 * Convert a byte array to a hexadecimal String
 **/
 public static String byteArrayToHexString(byte[] b) {
  String result = "";
  for(int i=0;i<b.length;++i)
   result += byteToHexString(b[i]); 
  return result;
 }
 /**
 * Convert a byte array to a base 64 string (see RFC 1421)
 **/
 public static String byteArrayToBase64String(byte[] b, int len) {
  String s = "";
  // Organize into three byte groups and convert
  int n = len / 3;
  int m = len % 3;
  for(int i=0; i<n; ++i) {
   int j = i*3;
   s += toBase64(b[j],b[j+1],b[j+2]);
  }
  if(m == 1) s += toBase64(b[len-1]);
  else if(m==2) s += toBase64(b[len-2],b[len-1]);
  // Insert a new line every 64 characters
  String result = "";
  len = s.length();
  n = len / 64;
  m = len % 64;
  for(int i=0; i<n; ++i) {
   result += s.substring(i*64,(i+1)*64) + "\n";
  }
  if(m > 0) result += s.substring(n*64,len) + "\n";
  return result;
 }
 /**
 * Convert a byte array to a base 64 string (see RFC 1421)
 **/
 public static String byteArrayToBase64String(byte[] b) {
  return byteArrayToBase64String(b,b.length);
 }
 /**
 * Perform the base64 transformation
 **/
 private static String toBase64(byte b1, byte b2, byte b3) {
  int[] digit = new int[4];
  digit[0] = (b1 & 0xFC) >>> 2;
  digit[1] = (b1 & 0x03) << 4;
  digit[1] |= (b2 & 0xF0) >> 4;
  digit[2] = (b2 & 0x0F) << 2;
  digit[2] |= (b3 & 0xC0) >> 6;
  digit[3] = (b3 & 0x3F);
  String result = "";
  for(int i=0;i<digit.length;++i) 
   result += base64Digit(digit[i]);
  return result;
 }
 /**
 * Perform a padded base64 transformation
 **/
 private static String toBase64(byte b1, byte b2) {
  int[] digit = new int[3];
  digit[0] = (b1 & 0xFC) >>> 2;
  digit[1] = (b1 & 0x03) << 4;
  digit[1] |= (b2 & 0xF0) >> 4;
  digit[2] = (b2 & 0x0F) << 2;
  String result = "";
  for(int i=0;i<digit.length;++i) 
   result += base64Digit(digit[i]);
  result += "=";
  return result;
 }
 /**
 *   Perform a padded base64 transformation
 **/
 private static String toBase64(byte b1) {
  int[] digit = new int[2];
  digit[0] = (b1 & 0xFC) >>> 2;
  digit[1] = (b1 & 0x03) << 4;
  String result = "";
  for(int i=0;i<digit.length;++i) 
   result += base64Digit(digit[i]);
  result += "==";
  return result;
 }
 private static char base64Digit(int i) {
  if(i<26) return (char) ('A' + i);
  if(i<52) return (char) ('a' + (i - 26));
  if(i<62) return (char) ('0' + (i - 52));
  if(i == 62) return '+';
  else return '/';
 }
 /**
 *  Convert a base 64 string to a byte array (see RFC 1421)
 **/
 public static byte[] base64StringToByteArray(String s)
   throws NumberFormatException {
  String t = "";
  for(int i=0;i<s.length();++i) {
   char c = s.charAt(i);
   if(c == '\n') continue;
   else if((c>='A' && c<='Z') || (c>='a' && c<='z') || 
     (c>='0' && c<='9') || c=='+' || c=='/') t += c;
   else if(c=='=') break;
   else throw new NumberFormatException();
  }
  int len = t.length();
  int n = 3*(len/4);
  switch(len % 4) {
  case 1:
   throw new NumberFormatException();
  case 2:
   len += 2;
   n += 1;
   t += "==";
   break;
  case 3:
   ++len;
   n += 2;
   t += "=";
   break;
  }
  byte[] b = new byte[n];
  for(int i=0; i < len/4; ++i) {
   byte[] temp = base64ToBytes(t.substring(4*i,4*(i+1)));
   for(int j=0;j<temp.length;++j) {
    b[3*i+j] = temp[j];
   }
  }
  return b;
 }
 private static byte[] base64ToBytes(String s) {
  int len = 0;
  for(int i=0;i<s.length();++i)
   if(s.charAt(i) != '=') ++len;
  int[] digit = new int[len];
  for(int i=0;i<len;++i) {
   char c = s.charAt(i);
   if(c>='A' && c<='Z') digit[i] = c - 'A';
   else if(c>='a' && c<='z') digit[i] = c - 'a' + 26;
   else if(c>='0' && c<='9') digit[i] = c - '0' + 52;
   else if(c=='+') digit[i] = 62;
   else if(c=='/') digit[i] = 63;   
  }
  byte[] b = new byte[len-1];
  switch(len) {
   case 4:
    b[2] = (byte) ((((digit[2]) & 0x03) << 6) | digit[3]);
   case 3:
    b[1] = (byte) ((((digit[1]) & 0x0F) << 4) | ((digit[2] & 0x3C) >>> 2));
   case 2:
    b[0] = (byte) ((digit[0] << 2) | ((digit[1] & 0x30) >>> 4));
  }
  return b;
 }
}