从博客中看出来我是个比较钟爱Java的应用密码学研究者。虽然C在密码学中有不可替代的优势：速度快，但是，Java的可移植性使得开发人员可以很快地将代码移植到各个平台，这比C实现要方便的多。尤其是Android平台的出现，Java的应用也就越来越广。因此，我本人在密码学研究过程中实际上也在逐渐使用和封装一些知名的Java密码学库，主要是方便自己使用。
Java JDK实际上自带了密码学库，支持几乎所有通用密码学原型的实现。然而，自带密码库有几个缺点：第一，由于版权问题，其并不支持全部的密码学原型，如256位的AES加密等等。第二，Java JDK的使用并非特别的方便。因此，我现在基本上在使用另一个知名的Java密码学库：Bouncy Castle，其官方网址为：http://www.bouncycastle.org/java.html。
但是，现在网上对于Bouncy Castle的介绍实在是有点少，而且每个人写的代码都不太一样，绝大多数人共享的代码只是为了个人使用，复用性并不是很强。因此，我现在在逐渐编写一些复用性比较强的封装，从而方便在自己设计的公钥加密、签名等体制中调用。
第一部分的实现是标准Hash算法。这一实现使用的是Java JDK，但是使用了Bouncy Castle的工具库实现Byte和String的一些转换。
在进入正题前，我先介绍一下自己引用或者实现的一些Util封装，这些封装会方便我进行下一步的实现。不管使用的方便与否，各位看官凑合着看，凑合着用，如果有任何可以改进的地方还请给我发邮件，我的邮箱是footman_900217@126.com。
这个In.java，包括下面的Out.java、StdIn.java以及StdOut.java都是从Princeton的算法公开课中使用的库函数。他们对Java的原始输入输出进行了进一步的封装，我个人认为非常好用。当然了，在实现过程中大家也可以使用JDK自带的函数库。Princeton的开发者们实际上对于其库函数封装了一个统一的jar文件，称为stdlib.jar。大家可以直接在工程中引用这个jar文件，或者下载源代码并放置在工程中。我是选择了后者，这主要是为了方便工程向Android中的移植，避免了jar文件引用过程中可能出现的一些错误。所有的源代码可以从下面的链接中下载到：http://algs4.cs.princeton.edu/home/。为了方便使用，在此我附上代码，但是注意这些代码的原始版权为Princeton大学。
import java.io.BufferedInputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.Socket;
import java.net.URL;
import java.net.URLConnection;
import java.util.Locale;
import java.util.Scanner;
/**
* <i>Input</i>. This class provides methods for reading strings
* and numbers from standard input, file input, URL, and socket.
* <p>
* The Locale used is: language = English, country = US. This is consistent
* with the formatting conventions with Java floating-point literals,
* command-line arguments (via <tt>Double.parseDouble()</tt>)
* and standard output (via <tt>System.out.print()</tt>). It ensures that
* standard input works the number formatting used in the textbook.
* <p>
* For additional documentation, see <a href="http://introcs.cs.princeton.edu/31datatype">Section 3.1</a> of
* <i>Introduction to Programming in Java: An Interdisciplinary Approach</i> by Robert Sedgewick and Kevin Wayne.
*/
public final class In {
private Scanner scanner;
// assume Unicode UTF-8 encoding
private final static String charsetName = "UTF-8";
// private final static String charsetName = "ISO-8859-1";
// assume language = English, country = US for consistency with System.out.
private Locale usLocale = new Locale("en", "US");
/**
* Create an input stream for standard input.
*/
public In() {
scanner = new Scanner(new BufferedInputStream(System.in), charsetName);
scanner.useLocale(usLocale);
}
/**
* Create an input stream from a socket.
*/
public In(Socket socket) {
try {
InputStream is = socket.getInputStream();
scanner = new Scanner(new BufferedInputStream(is), charsetName);
scanner.useLocale(usLocale);
}
catch (IOException ioe) {
System.err.println("Could not open " + socket);
}
}
/**
* Create an input stream from a URL.
*/
public In(URL url) {
try {
URLConnection site = url.openConnection();
InputStream is = site.getInputStream();
scanner = new Scanner(new BufferedInputStream(is), charsetName);
scanner.useLocale(usLocale);
}
catch (IOException ioe) {
System.err.println("Could not open " + url);
}
}
/**
* Create an input stream from a file.
*/
public In(File file) {
try {
scanner = new Scanner(file, charsetName);
scanner.useLocale(usLocale);
}
catch (IOException ioe) {
System.err.println("Could not open " + file);
}
}
/**
* Create an input stream from a filename or web page name.
*/
public In(String s) {
try {
// first try to read file from local file system
File file = new File(s);
if (file.exists()) {
scanner = new Scanner(file, charsetName);
scanner.useLocale(usLocale);
return;
}
// next try for files included in jar
URL url = getClass().getResource(s);
// or URL from web
if (url == null) { url = new URL(s); }
URLConnection site = url.openConnection();
InputStream is = site.getInputStream();
scanner = new Scanner(new BufferedInputStream(is), charsetName);
scanner.useLocale(usLocale);
}
catch (IOException ioe) {
System.err.println("Could not open " + s);
}
}
/**
* Does the input stream exist?
*/
public boolean exists() {
return scanner != null;
}
/**
* Is the input stream empty?
*/
public boolean isEmpty() {
return !scanner.hasNext();
}
/**
* Does the input stream have a next line?
*/
public boolean hasNextLine() {
return scanner.hasNextLine();
}
/**
* Read and return the next line.
*/
public String readLine() {
String line;
try { line = scanner.nextLine(); }
catch (Exception e) { line = null; }
return line;
}
/**
* Read and return the next character.
*/
public char readChar() {
// (?s) for DOTALL mode so . matches any character, including a line termination character
// 1 says look only one character ahead
// consider precompiling the pattern
String s = scanner.findWithinHorizon("(?s).", 1);
return s.charAt(0);
}
// return rest of input as string
/**
* Read and return the remainder of the input as a string.
*/
public String readAll() {
if (!scanner.hasNextLine()) { return null; }
// reference: http://weblogs.java.net/blog/pat/archive/2004/10/stupid_scanner_1.html
return scanner.useDelimiter("\\A").next();
}
/**
* Return the next string from the input stream.
*/
public String readString() {
return scanner.next();
}
/**
* Return the next int from the input stream.
*/
public int readInt() {
return scanner.nextInt();
}
/**
* Return the next double from the input stream.
*/
public double readDouble() {
return scanner.nextDouble();
}
/**
* Return the next float from the input stream.
*/
public double readFloat() {
return scanner.nextFloat();
}
/**
* Return the next long from the input stream.
*/
public long readLong() {
return scanner.nextLong();
}
/**
* Return the next byte from the input stream.
*/
public byte readByte() {
return scanner.nextByte();
}
/**
* Return the next boolean from the input stream, allowing "true" or "1"
* for true and "false" or "0" for false.
*/
public boolean readBoolean() {
String s = readString();
if (s.equalsIgnoreCase("true")) return true;
if (s.equalsIgnoreCase("false")) return false;
if (s.equals("1")) return true;
if (s.equals("0")) return false;
throw new java.util.InputMismatchException();
}
/**
* Read ints from file
*/
public static int[] readInts(String filename) {
In in = new In(filename);
String[] fields = in.readAll().trim().split("\\s+");
int[] vals = new int[fields.length];
for (int i = 0; i < fields.length; i++)
vals[i] = Integer.parseInt(fields[i]);
return vals;
}
/**
* Read doubles from file
*/
public static double[] readDoubles(String filename) {
In in = new In(filename);
String[] fields = in.readAll().trim().split("\\s+");
double[] vals = new double[fields.length];
for (int i = 0; i < fields.length; i++)
vals[i] = Double.parseDouble(fields[i]);
return vals;
}
/**
* Read strings from a file
*/
public static String[] readStrings(String filename) {
In in = new In(filename);
String[] fields = in.readAll().trim().split("\\s+");
return fields;
}
/**
* Read ints from standard input
*/
public static int[] readInts() {
In in = new In();
String[] fields = in.readAll().trim().split("\\s+");
int[] vals = new int[fields.length];
for (int i = 0; i < fields.length; i++)
vals[i] = Integer.parseInt(fields[i]);
return vals;
}
/**
* Read doubles from standard input
*/
public static double[] readDoubles() {
In in = new In();
String[] fields = in.readAll().trim().split("\\s+");
double[] vals = new double[fields.length];
for (int i = 0; i < fields.length; i++)
vals[i] = Double.parseDouble(fields[i]);
return vals;
}
/**
* Read strings from standard input
*/
public static String[] readStrings() {
In in = new In();
String[] fields = in.readAll().trim().split("\\s+");
return fields;
}
/**
* Close the input stream.
*/
public void close() { scanner.close(); }
/**
* Test client.
*/
public static void main(String[] args) {
In in;
String urlName = "http://introcs.cs.princeton.edu/stdlib/InTest.txt";
// read from a URL
System.out.println("readAll() from URL " + urlName);
System.out.println("---------------------------------------------------------------------------");
try {
in = new In(urlName);
System.out.println(in.readAll());
}
catch (Exception e) { System.out.println(e); }
System.out.println();
// read one line at a time from URL
System.out.println("readLine() from URL " + urlName);
System.out.println("---------------------------------------------------------------------------");
try {
in = new In(urlName);
while (!in.isEmpty()) {
String s = in.readLine();
System.out.println(s);
}
}
catch (Exception e) { System.out.println(e); }
System.out.println();
// read one string at a time from URL
System.out.println("readString() from URL " + urlName);
System.out.println("---------------------------------------------------------------------------");
try {
in = new In(urlName);
while (!in.isEmpty()) {
String s = in.readString();
System.out.println(s);
}
}
catch (Exception e) { System.out.println(e); }
System.out.println();
// read one line at a time from file in current directory
System.out.println("readLine() from current directory");
System.out.println("---------------------------------------------------------------------------");
try {
in = new In("./InTest.txt");
while (!in.isEmpty()) {
String s = in.readLine();
System.out.println(s);
}
}
catch (Exception e) { System.out.println(e); }
System.out.println();
// read one line at a time from file using relative path
System.out.println("readLine() from relative path");
System.out.println("---------------------------------------------------------------------------");
try {
in = new In("../stdlib/InTest.txt");
while (!in.isEmpty()) {
String s = in.readLine();
System.out.println(s);
}
}
catch (Exception e) { System.out.println(e); }
System.out.println();
// read one char at a time
System.out.println("readChar() from file");
System.out.println("---------------------------------------------------------------------------");
try {
in = new In("InTest.txt");
while (!in.isEmpty()) {
char c = in.readChar();
System.out.print(c);
}
}
catch (Exception e) { System.out.println(e); }
System.out.println();
System.out.println();
// read one line at a time from absolute OS X / Linux path
System.out.println("readLine() from absolute OS X / Linux path");
System.out.println("---------------------------------------------------------------------------");
in = new In("/n/fs/csweb/introcs/stdlib/InTest.txt");
try {
while (!in.isEmpty()) {
String s = in.readLine();
System.out.println(s);
}
}
catch (Exception e) { System.out.println(e); }
System.out.println();
// read one line at a time from absolute Windows path
System.out.println("readLine() from absolute Windows path");
System.out.println("---------------------------------------------------------------------------");
try {
in = new In("G:\\www\\introcs\\stdlib\\InTest.txt");
while (!in.isEmpty()) {
String s = in.readLine();
System.out.println(s);
}
System.out.println();
}
catch (Exception e) { System.out.println(e); }
System.out.println();
}
}
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Locale;
/**
* This class provides methods for writing strings and numbers to
* various output streams, including standard output, file, and sockets.
* <p>
* For additional documentation, see
* <a href="http://introcs.cs.princeton.edu/31datatype">Section 3.1</a> of
* <i>Introduction to Programming in Java: An Interdisciplinary Approach</i>
* by Robert Sedgewick and Kevin Wayne.
*/
public class Out {
// force Unicode UTF-8 encoding; otherwise it's system dependent
private static String charsetName = "UTF-8";
// assume language = English, country = US for consistency with In
private static final Locale US_LOCALE = new Locale("en", "US");
private PrintWriter out;
/**
* Create an Out object using an OutputStream.
*/
public Out(OutputStream os) {
try {
OutputStreamWriter osw = new OutputStreamWriter(os, charsetName);
out = new PrintWriter(osw, true);
}
catch (IOException e) { e.printStackTrace(); }
}
/**
* Create an Out object using standard output.
*/
public Out() { this(System.out); }
/**
* Create an Out object using a Socket.
*/
public Out(Socket socket) {
try {
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os, charsetName);
out = new PrintWriter(osw, true);
}
catch (IOException e) { e.printStackTrace(); }
}
/**
* Create an Out object using a file specified by the given name.
*/
public Out(String s) {
try {
OutputStream os = new FileOutputStream(s);
OutputStreamWriter osw = new OutputStreamWriter(os, charsetName);
out = new PrintWriter(osw, true);
}
catch (IOException e) { e.printStackTrace(); }
}
/**
* Close the output stream.
*/
public void close() { out.close(); }
/**
* Terminate the line.
*/
public void println() {
out.println();
}
/**
* Print an object and then terminate the line.
*/
public void println(Object x) {
out.println(x);
}
/**
* Print a boolean and then terminate the line.
*/
public void println(boolean x) {
out.println(x);
}
/**
* Print a char and then terminate the line.
*/
public void println(char x) {
out.println(x);
}
/**
* Print an double and then terminate the line.
*/
public void println(double x) {
out.println(x);
}
/**
* Print a float and then terminate the line.
*/
public void println(float x) {
out.println(x);
}
/**
* Print an int and then terminate the line.
*/
public void println(int x) {
out.println(x);
}
/**
* Print a long and then terminate the line.
*/
public void println(long x) {
out.println(x);
}
/**
* Print a byte and then terminate the line.
*/
public void println(byte x) {
out.println(x);
}
/**
* Flush the output stream.
*/
public void print() {
out.flush();
}
/**
* Print an object and then flush the output stream.
*/
public void print(Object x) {
out.print(x);
out.flush();
}
/**
* Print an boolean and then flush the output stream.
*/
public void print(boolean x) {
out.print(x);
out.flush();
}
/**
* Print an char and then flush the output stream.
*/
public void print(char x) {
out.print(x);
out.flush();
}
/**
* Print an double and then flush the output stream.
*/
public void print(double x) {
out.print(x);
out.flush();
}
/**
* Print a float and then flush the output stream.
*/
public void print(float x) {
out.print(x);
out.flush();
}
/**
* Print an int and then flush the output stream.
*/
public void print(int x) {
out.print(x);
out.flush();
}
/**
* Print a long and then flush the output stream.
*/
public void print(long x) {
out.print(x);
out.flush();
}
/**
* Print a byte and then flush the output stream.
*/
public void print(byte x) {
out.print(x);
out.flush();
}
/**
* Print a formatted string using the specified format string and arguments,
* and then flush the output stream.
*/
public void printf(String format, Object... args) {
out.printf(US_LOCALE, format, args);
out.flush();
}
/**
* Print a formatted string using the specified locale, format string and arguments,
* and then flush the output stream.
*/
public void printf(Locale locale, String format, Object... args) {
out.printf(locale, format, args);
out.flush();
}
/**
* A test client.
*/
public static void main(String[] args) {
Out out;
// write to stdout
out = new Out();
out.println("Test 1");
out.close();
// write to a file
out = new Out("test.txt");
out.println("Test 2");
out.close();
}
}
import java.io.BufferedInputStream;
import java.util.Locale;
import java.util.Scanner;
/**
* <i>Standard input</i>. This class provides methods for reading strings
* and numbers from standard input.
* <p>
* The Locale used is: language = English, country = US. This is consistent
* with the formatting conventions with Java floating-point literals,
* command-line arguments (via <tt>Double.parseDouble()</tt>)
* and standard output (via <tt>System.out.print()</tt>). It ensures that
* standard input works with the input files used in the textbook.
* <p>
* For additional documentation, see <a href="http://introcs.cs.princeton.edu/15inout">Section 1.5</a> of
* <i>Introduction to Programming in Java: An Interdisciplinary Approach</i> by Robert Sedgewick and Kevin Wayne.
*/
public final class StdIn {
// assume Unicode UTF-8 encoding
private static String charsetName = "UTF-8";
// assume language = English, country = US for consistency with System.out.
private static Locale usLocale = new Locale("en", "US");
// the scanner object
private static Scanner scanner = new Scanner(new BufferedInputStream(System.in), charsetName);
// static initializer
static { scanner.useLocale(usLocale); }
// don't instantiate
private StdIn() { }
/**
* Is there only whitespace left on standard input?
*/
public static boolean isEmpty() {
return !scanner.hasNext();
}
/**
* Return next string from standard input
*/
public static String readString() {
return scanner.next();
}
/**
* Return next int from standard input
*/
public static int readInt() {
return scanner.nextInt();
}
/**
* Return next double from standard input
*/
public static double readDouble() {
return scanner.nextDouble();
}
/**
* Return next float from standard input
*/
public static float readFloat() {
return scanner.nextFloat();
}
/**
* Return next short from standard input
*/
public static short readShort() {
return scanner.nextShort();
}
/**
* Return next long from standard input
*/
public static long readLong() {
return scanner.nextLong();
}
/**
* Return next byte from standard input
*/
public static byte readByte() {
return scanner.nextByte();
}
/**
* Return next boolean from standard input, allowing "true" or "1" for true,
* and "false" or "0" for false
*/
public static boolean readBoolean() {
String s = readString();
if (s.equalsIgnoreCase("true")) return true;
if (s.equalsIgnoreCase("false")) return false;
if (s.equals("1")) return true;
if (s.equals("0")) return false;
throw new java.util.InputMismatchException();
}
/**
* Does standard input have a next line?
*/
public static boolean hasNextLine() {
return scanner.hasNextLine();
}
/**
* Return rest of line from standard input
*/
public static String readLine() {
return scanner.nextLine();
}
/**
* Return next char from standard input
*/
// a complete hack and inefficient - email me if you have a better
public static char readChar() {
// (?s) for DOTALL mode so . matches a line termination character
// 1 says look only one character ahead
// consider precompiling the pattern
String s = scanner.findWithinHorizon("(?s).", 1);
return s.charAt(0);
}
/**
* Return rest of input from standard input
*/
public static String readAll() {
if (!scanner.hasNextLine()) return null;
// reference: http://weblogs.java.net/blog/pat/archive/2004/10/stupid_scanner_1.html
return scanner.useDelimiter("\\A").next();
}
/**
* Read rest of input as array of ints
*/
public static int[] readInts() {
String[] fields = readAll().trim().split("\\s+");
int[] vals = new int[fields.length];
for (int i = 0; i < fields.length; i++)
vals[i] = Integer.parseInt(fields[i]);
return vals;
}
/**
* Read rest of input as array of doubles
*/
public static double[] readDoubles() {
String[] fields = readAll().trim().split("\\s+");
double[] vals = new double[fields.length];
for (int i = 0; i < fields.length; i++)
vals[i] = Double.parseDouble(fields[i]);
return vals;
}
/**
* Read rest of input as array of strings
*/
public static String[] readStrings() {
String[] fields = readAll().trim().split("\\s+");
return fields;
}
/**
* Unit test
*/
public static void main(String[] args) {
System.out.println("Type a string: ");
String s = StdIn.readString();
System.out.println("Your string was: " + s);
System.out.println();
System.out.println("Type an int: ");
int a = StdIn.readInt();
System.out.println("Your int was: " + a);
System.out.println();
System.out.println("Type a boolean: ");
boolean b = StdIn.readBoolean();
System.out.println("Your boolean was: " + b);
System.out.println();
System.out.println("Type a double: ");
double c = StdIn.readDouble();
System.out.println("Your double was: " + c);
System.out.println();
}
}import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.util.Locale;
/**
* <i>Standard output</i>. This class provides methods for writing strings
* and numbers to standard output.
* <p>
* For additional documentation, see <a href="http://introcs.cs.princeton.edu/15inout">Section 1.5</a> of
* <i>Introduction to Programming in Java: An Interdisciplinary Approach</i> by Robert Sedgewick and Kevin Wayne.
*/
public final class StdOut {
// force Unicode UTF-8 encoding; otherwise it's system dependent
private static final String charsetName = "UTF-8";
// assume language = English, country = US for consistency with StdIn
private static final Locale US_LOCALE = new Locale("en", "US");
// send output here
private static PrintWriter out;
// this is called before invoking any methods
static {
try {
out = new PrintWriter(new OutputStreamWriter(System.out, charsetName), true);
}
catch (UnsupportedEncodingException e) { System.out.println(e); }
}
// don't instantiate
private StdOut() { }
// close the output stream (not required)
/**
* Close standard output.
*/
public static void close() {
out.close();
}
/**
* Terminate the current line by printing the line separator string.
*/
public static void println() {
out.println();
}
/**
* Print an object to standard output and then terminate the line.
*/
public static void println(Object x) {
out.println(x);
}
/**
* Print a boolean to standard output and then terminate the line.
*/
public static void println(boolean x) {
out.println(x);
}
/**
* Print a char to standard output and then terminate the line.
*/
public static void println(char x) {
out.println(x);
}
/**
* Print a double to standard output and then terminate the line.
*/
public static void println(double x) {
out.println(x);
}
/**
* Print a float to standard output and then terminate the line.
*/
public static void println(float x) {
out.println(x);
}
/**
* Print an int to standard output and then terminate the line.
*/
public static void println(int x) {
out.println(x);
}
/**
* Print a long to standard output and then terminate the line.
*/
public static void println(long x) {
out.println(x);
}
/**
* Print a short to standard output and then terminate the line.
*/
public static void println(short x) {
out.println(x);
}
/**
* Print a byte to standard output and then terminate the line.
*/
public static void println(byte x) {
out.println(x);
}
/**
* Flush standard output.
*/
public static void print() {
out.flush();
}
/**
* Print an Object to standard output and flush standard output.
*/
public static void print(Object x) {
out.print(x);
out.flush();
}
/**
* Print a boolean to standard output and flush standard output.
*/
public static void print(boolean x) {
out.print(x);
out.flush();
}
/**
* Print a char to standard output and flush standard output.
*/
public static void print(char x) {
out.print(x);
out.flush();
}
/**
* Print a double to standard output and flush standard output.
*/
public static void print(double x) {
out.print(x);
out.flush();
}
/**
* Print a float to standard output and flush standard output.
*/
public static void print(float x) {
out.print(x);
out.flush();
}
/**
* Print an int to standard output and flush standard output.
*/
public static void print(int x) {
out.print(x);
out.flush();
}
/**
* Print a long to standard output and flush standard output.
*/
public static void print(long x) {
out.print(x);
out.flush();
}
/**
* Print a short to standard output and flush standard output.
*/
public static void print(short x) {
out.print(x);
out.flush();
}
/**
* Print a byte to standard output and flush standard output.
*/
public static void print(byte x) {
out.print(x);
out.flush();
}
/**
* Print a formatted string to standard output using the specified
* format string and arguments, and flush standard output.
*/
public static void printf(String format, Object... args) {
out.printf(US_LOCALE, format, args);
out.flush();
}
/**
* Print a formatted string to standard output using the specified
* locale, format string, and arguments, and flush standard output.
*/
public static void printf(Locale locale, String format, Object... args) {
out.printf(locale, format, args);
out.flush();
}
// This method is just here to test the class
public static void main(String[] args) {
// write to stdout
StdOut.println("Test");
StdOut.println(17);
StdOut.println(true);
StdOut.printf("%.6f\n", 1.0/7.0);
}
}Timer.java主要是为了方便测试算法运行的时间。我简单地撰写了一个java文件进行测试，测试精读大概是纳秒级别的。在此需要提醒一下大家，System.nanoTime()返回的时间精度是非常高的，而System.currentTimeMillis()这个函数返回的结果精度只是毫秒级的，用于测试时间非常不精确，所以建议大家使用nanoTime()进行时间的测试。这个java文件还包括了一个nowTime()函数，用于返回当前的系统时间。这在我个人的开发中有一些用途。因为也属于时间函数，因此放在了Timer.java中。
import java.text.SimpleDateFormat;
import java.util.Date;
public class Timer {
public enum FORMAT{
SECOND, MILLI_SECOND, MICRO_SECOND, NANO_SECOND,
}
public static final int DEFAULT_MAX_NUM_TIMER = 10;
public final int MAX_NUM_TIMER;
private long[] timeRecorder;
private boolean[] isTimerStart;
private FORMAT[] outFormat;
public static String nowTime() {
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss");// 设置日期格式
return df.format(new Date());
}
public Timer(){
this.MAX_NUM_TIMER = DEFAULT_MAX_NUM_TIMER;
this.timeRecorder = new long[MAX_NUM_TIMER];
this.isTimerStart = new boolean[MAX_NUM_TIMER];
this.outFormat = new FORMAT[MAX_NUM_TIMER];
//set default format as millisecond
for (int i=0; i<outFormat.length; i++){
outFormat[i] = FORMAT.MILLI_SECOND;
}
}
public Timer(int max_num_timer){
this.MAX_NUM_TIMER = max_num_timer;
this.timeRecorder = new long[MAX_NUM_TIMER];
this.isTimerStart = new boolean[MAX_NUM_TIMER];
this.outFormat = new FORMAT[MAX_NUM_TIMER];
//set default format as millisecond
for (int i=0; i<outFormat.length; i++){
outFormat[i] = FORMAT.MILLI_SECOND;
}
}
public void setFormat(int num, FORMAT format){
//Ensure num less than MAX_NUM_TIMER
assert(num >=0 && num < MAX_NUM_TIMER);
this.outFormat[num] = format;
}
public void start(int num) {
//Ensure the timer now stops.
assert(!isTimerStart[num]);
//Ensure num less than MAX_NUM_TIMER
assert(num >=0 && num < MAX_NUM_TIMER);
isTimerStart[num] = true;
timeRecorder[num] = System.nanoTime();
}
public double stop(int num) {
//Ensure the timer now starts.
assert(isTimerStart[num]);
//Ensure num less than MAX_NUM_TIMER
assert(num >=0 && num < MAX_NUM_TIMER);
long result = System.nanoTime() - timeRecorder[num];
isTimerStart[num] = false;
switch(outFormat[num]){
case SECOND:
return (double) result / 1000000000L;
case MILLI_SECOND:
return (double) result / 1000000L;
case MICRO_SECOND:
return (double) result / 1000L;
case NANO_SECOND:
return (double) result;
default:
return (double) result / 1000000L;
}
}
}Hash函数是将任意长的子串M映射成一个较短的定长输出子串H的函数，这个函数一般用h或者hash表示。我们要求h(M)必须易于计算，称H=h(M)为M的Hash值。h函数是一个多对一的映射，一般为了安全性，我们要求很难从H求出原来的M，或者从H求出一个M‘，使得h(M)=h(M‘)。但是，我们可以验证任意给定子串M‘是否与M具有相同的Hash值。
Hash函数可以按照是否有密钥作为输入分为两大类。一类有密钥控制，即函数定义为h(k, M)；另一类没有密钥控制，任何人都可以计算，即函数定义为h(M)。因此，h(k, M)只有拥有密钥的人可以计算，所以其一般具有身份认证功能；h(M)任何人都可以计算，因而不具有身份认证的功能，只用于检测接收数据的完整性，或者验证输入的内容是否为原始输入的内容。
对于第一类Hash函数，在此我并不涉及，因为其函数一般来说是通过第二类Hash函数与单钥加密函数合并实现的，因此我把单钥加密函数以及第二类Hash函数作为密码学原型函数，而把第一类Hash函数看做他们的一种扩展。对于第二类Hash函数，比较知名的，或者说大家都知道的有MD5，SHA1等等。但是实际上，MD5和SHA1已经被认为并不安全，攻破的人正是清华大学著名的密码学家王小云老师。因此，在这里我也不涉及MD5，SHA1的实现，而涉及到的是SHA256，SHA384，SHA512的实现。说句题外话，我有幸与王小云老师有过三面之缘，王小云老师确实是一个典型的数学家，有着非常严谨的思维，她的团队现在致力于Lattice有限域结构的研究。如果看官有兴趣读王小云老师的博士，可以联系她，她人很nice的~
在密码学中，Hash函数需要满足如下形式：
一般来说，应用典型的生日攻击（birthday attack，http://zh.wikipedia.org/wiki/%E7%94%9F%E6%97%A5%E5%95%8F%E9%A1%8C），我们可以将hash的安全常数降低一半。比如对于MD5，我们可以有1/2的概率，以2^80的计算量，找到一组数x和y，使得h(x)=h(y)，这就使得Hash函数不满足抗碰撞攻击。这种攻击对于任何Hash函数都是可行的。因此，一般来说Hash函数的安全常数是其输出长度的一半。如果一个Hash函数被证明其可以在比安全常数低的运算下能够找到碰撞，我们则称这个算法是不安全的。王小云老师的结果是，对于MD5算法，其甚至已经不能抗原像攻击。而对于SHA1算法，其安全性已经降低到69，已经不安全。
其实Hash函数的实现比较简单。不过为了具有重用性，我们要求写出的函数既能够对任意byte[]数组进行Hash，也能够对于任意的InputStream进行Hash。针对不同的算法，我写了一个封装，其class名称为GeneralHash（这是为了后面的GroupHash实现而区分），源代码如下：
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import org.bouncycastle.util.encoders.Hex;
import cn.edu.buaa.crypto.util.StdOut;
public class GeneralHash {
public enum HashMode{
SHA256,
SHA384,
SHA512,
}
private static final int DEFAULT_BLOCK_SIZE = 1024;
public static byte[] Hash(HashMode hashMode, byte[] message){
MessageDigest md = null;
try{
switch(hashMode){
case SHA256:
md = MessageDigest.getInstance("SHA-256");
break;
case SHA384:
md = MessageDigest.getInstance("SHA-384");
break;
case SHA512:
md = MessageDigest.getInstance("SHA-512");
break;
default:
//Default Hash is SHA256
md = MessageDigest.getInstance("SHA-256");
break;
}
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
}
md.update(message);
return md.digest();
}
public static byte[] Hash(HashMode hashMode, InputStream in){
MessageDigest md = null;
try{
switch(hashMode){
case SHA256:
md = MessageDigest.getInstance("SHA-256");
break;
case SHA384:
md = MessageDigest.getInstance("SHA-384");
break;
case SHA512:
md = MessageDigest.getInstance("SHA-512");
break;
default:
//Default Hash is SHA256
md = MessageDigest.getInstance("SHA-256");
break;
}
int inL;
byte[] b = new byte[DEFAULT_BLOCK_SIZE];
while ((inL = in.read(b)) != -1) {
md.update(b, 0, inL);
}
} catch (IOException e) {
e.printStackTrace();
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
}
return md.digest();
}
} private static void Test_Hash_String(){
String message1 = "TestGeneralHash-1";
String message2 = "TestGeneralHash-2";
byte[] byte256 = GeneralHash.Hash(HashMode.SHA256, message1.getBytes());
String sha256 = new String(Hex.encode(byte256));
StdOut.println("SHA256, message = " + message1);
StdOut.println("Result = " + sha256 + ", length = " + byte256.length);
//Hash result for the same value should be equal
byte[] byte256_1 = GeneralHash.Hash(HashMode.SHA256, message1.getBytes());
String sha256_1 = new String(Hex.encode(byte256_1));
StdOut.println("SHA256, message = " + message1);
StdOut.println("Result = " + sha256_1 + ", length = " + byte256_1.length);
assert(sha256.equals(sha256_1));
//Hash result for different values should be distinct
byte[] byte256_2 = GeneralHash.Hash(HashMode.SHA256, message2.getBytes());
String sha256_2 = new String(Hex.encode(byte256_2));
StdOut.println("SHA256, message = " + message2);
StdOut.println("Result = " + sha256_2 + ", length = " + byte256_2.length);
StdOut.println();
assert(!sha256.equals(sha256_2));
byte[] byte384 = GeneralHash.Hash(HashMode.SHA384, message1.getBytes());
String sha384 = new String(Hex.encode(byte384));
StdOut.println("SHA384, message = " + message1);
StdOut.println("Result = " + sha384 + ", length = " + byte384.length);
//Hash result for the same value should be equal
byte[] byte384_1 = GeneralHash.Hash(HashMode.SHA384, message1.getBytes());
String sha384_1 = new String(Hex.encode(byte384_1));
StdOut.println("SHA384, message = " + message1);
StdOut.println("Result = " + sha384_1 + ", length = " + byte384_1.length);
assert(sha384.equals(sha384_1));
//Hash result for different values should be distinct
byte[] byte384_2 = GeneralHash.Hash(HashMode.SHA384, message2.getBytes());
String sha384_2 = new String(Hex.encode(byte384_2));
StdOut.println("SHA384, message = " + message2);
StdOut.println("Result = " + sha384_2 + ", length = " + byte384_2.length);
StdOut.println();
assert(!sha384.equals(sha384_2));
byte[] byte512 = GeneralHash.Hash(HashMode.SHA512, message1.getBytes());
String sha512 = new String(Hex.encode(byte512));
StdOut.println("SHA512, message = " + message1);
StdOut.println("Result = " + sha512 + ", length = " + byte512.length);
//Hash result for the same value should be equal
byte[] byte512_1 = GeneralHash.Hash(HashMode.SHA512, message1.getBytes());
String sha512_1 = new String(Hex.encode(byte512_1));
StdOut.println("SHA512, message = " + message1);
StdOut.println("Result = " + sha512_1 + ", length = " + byte512_1.length);
assert(sha512.equals(sha512_1));
//Hash result for different values should be distinct
byte[] byte512_2 = GeneralHash.Hash(HashMode.SHA512, message2.getBytes());
String sha512_2 = new String(Hex.encode(byte512_2));
StdOut.println("SHA512, message = " + message2);
StdOut.println("Result = " + sha512_2 + ", length = " + byte512_2.length);
StdOut.println();
assert(!sha512.equals(sha512_2));
}
private static void Test_Hash_File(){
try {
File fileIn = new File("docs1.5on.zip");
FileInputStream in;
in = new FileInputStream(fileIn);
byte[] byte256 = GeneralHash.Hash(HashMode.SHA256, in);
String sha256 = new String(Hex.encode(byte256));
StdOut.println("File SHA256 = " + sha256 + ", length = " + byte256.length);
in.close();
in = new FileInputStream(fileIn);
byte[] byte384 = GeneralHash.Hash(HashMode.SHA384, in);
String sha384 = new String(Hex.encode(byte384));
StdOut.println("File SHA384 = " + sha384 + ", length = " + byte384.length);
in.close();
in = new FileInputStream(fileIn);
byte[] byte512 = GeneralHash.Hash(HashMode.SHA512, in);
String sha512 = new String(Hex.encode(byte512));
StdOut.println("File SHA512 = " + sha512 + ", length = " + byte512.length);
in.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public static void main(String[] args){
Test_Hash_String();
Test_Hash_File();
}Java密码学原型算法实现——第一部分：标准Hash算法,布布扣,bubuko.com
原文：http://blog.csdn.net/liuweiran900217/article/details/38406257