Md5 Hashing in Android

MD5 hashing in Android

Here is an implementation you can use (updated to use more up to date Java conventions - for:each loop, StringBuilder instead of StringBuffer):

public static String md5(final String s) {
    final String MD5 = "MD5";
    try {
        // Create MD5 Hash
        MessageDigest digest = java.security.MessageDigest
                .getInstance(MD5);
        digest.update(s.getBytes());
        byte messageDigest[] = digest.digest();

        // Create Hex String
        StringBuilder hexString = new StringBuilder();
        for (byte aMessageDigest : messageDigest) {
            String h = Integer.toHexString(0xFF & aMessageDigest);
            while (h.length() < 2)
                h = "0" + h;
            hexString.append(h);
        }
        return hexString.toString();

    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    }
    return "";
}

Although it is not recommended for systems that involve even the basic level of security (MD5 is considered broken and can be easily exploited), it is sometimes enough for basic tasks.

MD5 hash in android or java

The second web site is simply using base64 instead of hex to represent the binary data as text. So you can get rid of your bytesToHex method entirely, and just use Base64:

String base64Digest = Base64.encodeToString(thedigest, Base64.DEFAULT);

(As an aside, I'd avoid using the as a prefix in variable names - it provides no benefit, and is just cruft.)

How to Generate an MD5 hash in Kotlin?

Using java.security.MessageDigest is the simplest way

import java.math.BigInteger
import java.security.MessageDigest

fun md5(input:String): String {
    val md = MessageDigest.getInstance("MD5")
    return BigInteger(1, md.digest(input.toByteArray())).toString(16).padStart(32, '0')
}

how MD5 signature affects the app security?

MD5 was intended to provide integrity, not security. MD5 is a checksum, so It is supposed to be a short representation of potentionally infinite data. If you have a 1GB file, create an MD5 hash of it and flip a single bit within the 1GB file, the MD5 completly changes.

You will need the 1GB file, to calculate the MD5, you cannot get the 1GB file from the MD5.
I write intended since MD5 is concidered broken, an attacker could potentionally create content that is aimed to produce the same MD5.

Returning wrong md5 hash in jni

I have resolved my problem by replace:

typedef unsigned long int UINT4; in md5.c -> typedef uint32_t UINT4;.

I tested again on two device and it's work fine. On a 64 bits machine long int are (usually) 64 bits long instead of 32

How to generate an MD5 checksum for a file in Android?

Convert the file content into string & use the below method:

public static String getMD5EncryptedString(String encTarget){
        MessageDigest mdEnc = null;
        try {
            mdEnc = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            System.out.println("Exception while encrypting to md5");
            e.printStackTrace();
        } // Encryption algorithm
        mdEnc.update(encTarget.getBytes(), 0, encTarget.length());
        String md5 = new BigInteger(1, mdEnc.digest()).toString(16);
        while ( md5.length() < 32 ) {
            md5 = "0"+md5;
        }
        return md5;
    }

Note that this simple approach is suitable for smallish strings, but will not be efficient for large files. For the latter, see dentex's answer.

How can I generate an MD5 hash in Java?

You need java.security.MessageDigest.

Call MessageDigest.getInstance("MD5") to get a MD5 instance of MessageDigest you can use.

The compute the hash by doing one of:

• Feed the entire input as a byte[] and calculate the hash in one operation with md.digest(bytes).
• Feed the MessageDigest one byte[] chunk at a time by calling md.update(bytes). When you're done adding input bytes, calculate the hash with
  md.digest().

The byte[] returned by md.digest() is the MD5 hash.

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