Get MD5 String from Message Digest

Question

I understand how it works but if I want to print out the MD5 as String how would I do that?

public static void getMD5(String fileName) throws Exception{
    InputStream input =  new FileInputStream(fileName);
    byte[] buffer = new byte[1024];

    MessageDigest hash = MessageDigest.getInstance("MD5");
    int read;
    do {
        read = input.read(buffer);
        if (read > 0) {
            hash.update(buffer, 0, read);
        }
    } while (read != -1);
    input.close();
}

score 79 · Answer 1 · answered Sep 20 '12 at 14:06

79

You can get it writing less:

String hex = (new HexBinaryAdapter()).marshal(md5.digest(YOUR_STRING.getBytes()))

answered Sep 20 '12 at 14:06

arutaku

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1

Do you know if there are any performance considerations here? Assuming we reused a single HexBinaryAdapter, would this introduce any significant overheads compared to doing the bit operations ourselves? We need to use this code a lot as we use the MD5 for URLs as the key into our image cache. – Dan J Dec 18 '12 at 22:09
14

Java's source is public. :) `HexBinaryAdapter.marshal()` only calls `DatatypeConverter.printHexBinary()` (you can actually use that instead, if you want to avoid instantiating a `HexBinaryAdapter`), which in turn instantiates a singleton `DatatypeConverterImpl` the first time it's called. After that, it's just a straight call to `DatatypeConverterImpl`'s `printHexBinary`. It uses a method pretty similar to WhiteFang34's answer. – mpontes Mar 22 '13 at 19:01
5

HexBinaryAdapter is not in JDK9 – user1133275 Aug 30 '17 at 21:49

stacker · Answer 2 · 2014-07-10T14:09:07.020

29

    String input = "168";
    MessageDigest md = MessageDigest.getInstance("MD5");
    byte[] md5sum = md.digest(input.getBytes());
    String output = String.format("%032X", new BigInteger(1, md5sum));

or

DatatypeConverter.printHexBinary( MessageDigest.getInstance("MD5").digest("a".getBytes("UTF-8")))

edited Jul 10 '14 at 14:09

answered Mar 29 '11 at 09:16

stacker

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DatatypeConverter is not in JDK9 – user1133275 Aug 30 '17 at 21:02
@user1133275 See https://stackoverflow.com/questions/43574426/how-to-resolve-java-lang-noclassdeffounderror-javax-xml-bind-jaxbexception-in-j – stacker Aug 31 '17 at 05:33
yah I was just looking at that temporary hack for a lib, but for this question answers that do not depend on deprecated code are better. – user1133275 Aug 31 '17 at 14:13
1

BigInteger seems to have an issue when the leading hex digit is 0. – harley Nov 04 '18 at 21:15

score 23 · Accepted Answer · edited Oct 28 '15 at 12:18

23

Try this

StringBuffer hexString = new StringBuffer();
MessageDigest md = MessageDigest.getInstance("MD5");
byte[] hash = md.digest();

for (int i = 0; i < hash.length; i++) {
    if ((0xff & hash[i]) < 0x10) {
        hexString.append("0"
                + Integer.toHexString((0xFF & hash[i])));
    } else {
        hexString.append(Integer.toHexString(0xFF & hash[i]));
    }
}

edited Oct 28 '15 at 12:18

Willi Mentzel

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answered Mar 29 '11 at 09:15

ajm

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Note also that StringBuilder can be now used instead of StringBuffer, cons and pros of each are discussed in this question: http://stackoverflow.com/questions/355089/stringbuilder-and-stringbuffer – FanaticD Sep 22 '15 at 17:31

score 23 · Answer 4 · answered Mar 29 '11 at 09:20

23

You can also use Apache Commons Codec library. This library includes methods public static String md5Hex(InputStream data) and public static String md5Hex(byte[] data) in the DigestUtils class. No need to invent this yourself ;)

answered Mar 29 '11 at 09:20

mmjmanders

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score 9 · Answer 5 · answered Mar 29 '11 at 09:15

9

First you need to get the byte[] output of the MessageDigest:

byte[] bytes = hash.digest();

You can't easily print this though (with e.g. new String(bytes)) because it's going to contain binary that won't have good output representations. You can convert it to hex for display like this however:

StringBuilder sb = new StringBuilder(2 * bytes.length);
for (byte b : bytes) {
    sb.append("0123456789ABCDEF".charAt((b & 0xF0) >> 4));
    sb.append("0123456789ABCDEF".charAt((b & 0x0F)));
}
String hex = sb.toString();

answered Mar 29 '11 at 09:15

WhiteFang34

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Thanks for mentioning the actual problem, and what would come as a first thought in byte-string which is to just use the string constructor. Also, I'm surprised no one suggested Base64. How does Base64 compare to these HexToBinary answers. – Teddy Apr 06 '21 at 15:22
Found this: https://stackoverflow.com/a/3183880/1364747 – Teddy Apr 06 '21 at 15:24

score 7 · Answer 6 · answered Dec 16 '18 at 18:23

7

Shortest way:

String toMD5(String input) {
    MessageDigest md = MessageDigest.getInstance("MD5");
    byte[] raw = md.digest(input.getBytes());
    return DatatypeConverter.printHexBinary(raw);
}

Just remember to handle the exception.

answered Dec 16 '18 at 18:23

Nguyen Le Vu Long

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carlao2005 · Answer 7 · 2016-05-20T15:20:25.033

4

With the byte array, result from message digest:

...
byte hashgerado[] = md.digest(entrada);
...

for(byte b : hashgerado)
    System.out.printf("%02x", Byte.toUnsignedInt(b));

Result (for example):
89e8a9f68ad3c4bba9b9d3581cf5201d

edited May 20 '16 at 15:20

answered May 20 '16 at 04:28

carlao2005

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score 2 · Answer 8 · answered Dec 10 '15 at 19:35

/**
 * hashes:
 * e7cfa2be5969e235138356a54bad7fc4
 * 3c9ec110aa171b57bb41fc761130822c
 *
 * compiled with java 8 - 12 Dec 2015
 */
public static String generateHash() {
    long r = new java.util.Random().nextLong();
    String input = String.valueOf(r);
    String md5 = null;

    try {
        java.security.MessageDigest digest = java.security.MessageDigest.getInstance("MD5");
        //Update input string in message digest
        digest.update(input.getBytes(), 0, input.length());
        //Converts message digest value in base 16 (hex)
        md5 = new java.math.BigInteger(1, digest.digest()).toString(16);
    }
    catch (java.security.NoSuchAlgorithmException e) {
        e.printStackTrace();
    }
    return md5;
}

score 2 · Answer 9 · answered Feb 27 '16 at 00:32

2

FYI...

In certain situations this did not work for me

md5 = new java.math.BigInteger(1, digest.digest()).toString(16);

but this did

StringBuilder sb = new StringBuilder();

for (int i = 0; i < digest.length; i++) {
    if ((0xff & digest[i]) < 0x10) {
        sb.append("0").append(Integer.toHexString((0xFF & digest[i])));
    } else {
        sb.append(Integer.toHexString(0xFF & digest[i]));
    }
}

String result = sb.toString();

answered Feb 27 '16 at 00:32

Will Berger

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Welcome to Stack Overflow, @WillBerger ! While this code may answer the question, providing additional context regarding how and/or why it solves the problem would improve the answer's long-term value. – mech Feb 27 '16 at 00:44

score -1 · Answer 10 · edited Sep 26 '14 at 16:22

-1

Call hash.digest() to finish the process. It will return an array of bytes.

You can create a String from a byte[] using a String constructor, however if you want a hex string you'll have to loop through the byte array manually and work out the characters.

edited Sep 26 '14 at 16:22

Priidu Neemre

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answered Mar 29 '11 at 09:14

brain

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score -2 · Answer 11 · answered Nov 14 '14 at 14:25

This is another version of @anything answer:

StringBuilder sb = new StringBuilder();

for (int i = 0; i < digest.length; i++) {
    if ((0xff & digest[i]) < 0x10) {
        sb.append("0").append(Integer.toHexString((0xFF & digest[i])));
    } else {
        sb.append(Integer.toHexString(0xFF & digest[i]));
    }
}

String result = sb.toString();

Get MD5 String from Message Digest

11 Answers11

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