在Java中是否有任何方法可以生成一个字符串的MD5哈希?
当前回答
MessageDigest类可以为您提供MD5摘要的实例。
当使用字符串和加密类时，请确保始终指定您希望字节表示的编码。如果只使用string.getBytes()，它将使用平台默认值。(并非所有平台都使用相同的默认值)
import java.security.*;
..
byte[] bytesOfMessage = yourString.getBytes("UTF-8");
MessageDigest md = MessageDigest.getInstance("MD5");
byte[] theMD5digest = md.digest(bytesOfMessage);
如果你有很多数据，看看.update(xxx)方法，它可以被重复调用。然后调用.digest()来获得结果散列。
其他回答
另一个选择是使用Guava哈希方法:
Hasher hasher = Hashing.md5().newHasher();
hasher.putString("my string");
byte[] md5 = hasher.hash().asBytes();
如果你已经在用番石榴，这很方便(如果你没有，你可能应该用)。
是我做的…似乎还行-我相信有人会指出错误…
public final class MD5 {
public enum SaltOption {
BEFORE, AFTER, BOTH, NONE;
}
private static final String ALG = "MD5";
//For conversion to 2-char hex
private static final char[] digits = {
'0' , '1' , '2' , '3' , '4' , '5' ,
'6' , '7' , '8' , '9' , 'a' , 'b' ,
'c' , 'd' , 'e' , 'f' , 'g' , 'h' ,
'i' , 'j' , 'k' , 'l' , 'm' , 'n' ,
'o' , 'p' , 'q' , 'r' , 's' , 't' ,
'u' , 'v' , 'w' , 'x' , 'y' , 'z'
};
private SaltOption opt;
/**
* Added the SaltOption constructor since everybody
* has their own standards when it comes to salting
* hashes.
*
* This gives the developer the option...
*
* @param option The salt option to use, BEFORE, AFTER, BOTH or NONE.
*/
public MD5(final SaltOption option) {
//TODO: Add Char Encoding options too... I was too lazy!
this.opt = option;
}
/**
*
* Returns the salted MD5 checksum of the text passed in as an argument.
*
* If the salt is an empty byte array - no salt is applied.
*
* @param txt The text to run through the MD5 algorithm.
* @param salt The salt value in bytes.
* @return The salted MD5 checksum as a <code>byte[]</code>
* @throws NoSuchAlgorithmException
*/
private byte[] createChecksum(final String txt, final byte[] salt) throws NoSuchAlgorithmException {
final MessageDigest complete = MessageDigest.getInstance(ALG);
if(opt.equals(SaltOption.BEFORE) || opt.equals(SaltOption.BOTH)) {
complete.update(salt);
}
complete.update(txt.getBytes());
if(opt.equals(SaltOption.AFTER) || opt.equals(SaltOption.BOTH)) {
complete.update(salt);
}
return complete.digest();
}
/**
*
* Returns the salted MD5 checksum of the file passed in as an argument.
*
* If the salt is an empty byte array - no salt is applied.
*
* @param fle The file to run through the MD5 algorithm.
* @param salt The salt value in bytes.
* @return The salted MD5 checksum as a <code>byte[]</code>
* @throws IOException
* @throws NoSuchAlgorithmException
*/
private byte[] createChecksum(final File fle, final byte[] salt)
throws IOException, NoSuchAlgorithmException {
final byte[] buffer = new byte[1024];
final MessageDigest complete = MessageDigest.getInstance(ALG);
if(opt.equals(SaltOption.BEFORE) || opt.equals(SaltOption.BOTH)) {
complete.update(salt);
}
int numRead;
InputStream fis = null;
try {
fis = new FileInputStream(fle);
do {
numRead = fis.read(buffer);
if (numRead > 0) {
complete.update(buffer, 0, numRead);
}
} while (numRead != -1);
} finally {
if (fis != null) {
fis.close();
}
}
if(opt.equals(SaltOption.AFTER) || opt.equals(SaltOption.BOTH)) {
complete.update(salt);
}
return complete.digest();
}
/**
*
* Efficiently converts a byte array to its 2 char per byte hex equivalent.
*
* This was adapted from JDK code in the Integer class, I just didn't like
* having to use substrings once I got the result...
*
* @param b The byte array to convert
* @return The converted String, 2 chars per byte...
*/
private String convertToHex(final byte[] b) {
int x;
int charPos;
int radix;
int mask;
final char[] buf = new char[32];
final char[] tmp = new char[3];
final StringBuilder md5 = new StringBuilder();
for (int i = 0; i < b.length; i++) {
x = (b[i] & 0xFF) | 0x100;
charPos = 32;
radix = 1 << 4;
mask = radix - 1;
do {
buf[--charPos] = digits[x & mask];
x >>>= 4;
} while (x != 0);
System.arraycopy(buf, charPos, tmp, 0, (32 - charPos));
md5.append(Arrays.copyOfRange(tmp, 1, 3));
}
return md5.toString();
}
/**
*
* Returns the salted MD5 checksum of the file passed in as an argument.
*
* @param fle The file you want want to run through the MD5 algorithm.
* @param salt The salt value in bytes
* @return The salted MD5 checksum as a 2 char per byte HEX <code>String</code>
* @throws NoSuchAlgorithmException
* @throws IOException
*/
public String getMD5Checksum(final File fle, final byte[] salt)
throws NoSuchAlgorithmException, IOException {
return convertToHex(createChecksum(fle, salt));
}
/**
*
* Returns the MD5 checksum of the file passed in as an argument.
*
* @param fle The file you want want to run through the MD5 algorithm.
* @return The MD5 checksum as a 2 char per byte HEX <code>String</code>
* @throws NoSuchAlgorithmException
* @throws IOException
*/
public String getMD5Checksum(final File fle)
throws NoSuchAlgorithmException, IOException {
return convertToHex(createChecksum(fle, new byte[0]));
}
/**
*
* Returns the salted MD5 checksum of the text passed in as an argument.
*
* @param txt The text you want want to run through the MD5 algorithm.
* @param salt The salt value in bytes.
* @return The salted MD5 checksum as a 2 char per byte HEX <code>String</code>
* @throws NoSuchAlgorithmException
* @throws IOException
*/
public String getMD5Checksum(final String txt, final byte[] salt)
throws NoSuchAlgorithmException {
return convertToHex(createChecksum(txt, salt));
}
/**
*
* Returns the MD5 checksum of the text passed in as an argument.
*
* @param txt The text you want want to run through the MD5 algorithm.
* @return The MD5 checksum as a 2 char per byte HEX <code>String</code>
* @throws NoSuchAlgorithmException
* @throws IOException
*/
public String getMD5Checksum(final String txt)
throws NoSuchAlgorithmException {
return convertToHex(createChecksum(txt, new byte[0]));
}
}
我已经使用php，如下所示
<?php
$goodtext = "Not found";
// If there is no parameter, this code is all skipped
if ( isset($_GET['md5']) ) {
$time_pre = microtime(true);
$md5 = $_GET['md5'];
// This is our alphabet
$txt = "0123456789";
$show = 15;
// Outer loop go go through the alphabet for the
// first position in our "possible" pre-hash
// text
for($i=0; $i<strlen($txt); $i++ ) {
$ch1 = $txt[$i]; // The first of two characters
// Our inner loop Note the use of new variables
// $j and $ch2
for($j=0; $j<strlen($txt); $j++ ) {
$ch2 = $txt[$j]; // Our second character
for($k=0; $k<strlen($txt); $k++ ) {
$ch3 = $txt[$k];
for($l=0; $l<strlen($txt); $l++){
$ch4 = $txt[$l];
// Concatenate the two characters together to
// form the "possible" pre-hash text
$try = $ch1.$ch2.$ch3.$ch4;
// Run the hash and then check to see if we match
$check = hash('md5', $try);
if ( $check == $md5 ) {
$goodtext = $try;
break; // Exit the inner loop
}
// Debug output until $show hits 0
if ( $show > 0 ) {
print "$check $try\n";
$show = $show - 1;
}
if($goodtext == $try){
break;
}
}
if($goodtext == $try){
break;
}
}
if($goodtext == $try) {
break;
}
}
if($goodtext == $try){
break;
}
}
// Compute ellapsed time
$time_post = microtime(true);
print "Ellapsed time: ";
print $time_post-$time_pre;
print "\n";
}
?>
你可以参考这个资料来源
找到了这个解决方案，在从MD5哈希中获得String表示形式方面要干净得多。
import java.security.*;
import java.math.*;
public class MD5 {
public static void main(String args[]) throws Exception{
String s="This is a test";
MessageDigest m=MessageDigest.getInstance("MD5");
m.update(s.getBytes(),0,s.length());
System.out.println("MD5: "+new BigInteger(1,m.digest()).toString(16));
}
}
代码是从这里提取出来的。
MessageDigest类可以为您提供MD5摘要的实例。
当使用字符串和加密类时，请确保始终指定您希望字节表示的编码。如果只使用string.getBytes()，它将使用平台默认值。(并非所有平台都使用相同的默认值)
import java.security.*;
..
byte[] bytesOfMessage = yourString.getBytes("UTF-8");
MessageDigest md = MessageDigest.getInstance("MD5");
byte[] theMD5digest = md.digest(bytesOfMessage);
如果你有很多数据，看看.update(xxx)方法，它可以被重复调用。然后调用.digest()来获得结果散列。
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