Hash String via SHA-256 in Java

Question

By looking around here as well as the internet in general, I have found Bouncy Castle. I want to use Bouncy Castle (or some other freely available utility) to generate a SHA-256 Hash of a String in Java. Looking at their documentation I can't seem to find any good examples of what I want to do. Can anybody here help me out?

Answer 1

I suppose you are using a relatively old Java Version without SHA-256. So you must add the BouncyCastle Provider to the already provided 'Security Providers' in your java version.

    // NEEDED if you are using a Java version without SHA-256    
    Security.addProvider(new BouncyCastleProvider());

    // then go as usual 
    MessageDigest md = MessageDigest.getInstance("SHA-256");
    String text = "my string...";
    md.update(text.getBytes("UTF-8")); // or UTF-16 if needed
    byte[] digest = md.digest();

Answer 2

This will work with "org.bouncycastle.util.encoders.Hex" following package

return new String(Hex.encode(digest));

Its in bouncycastle jar.

Answer 3

Java 8: Base64 available:

    MessageDigest md = MessageDigest.getInstance( "SHA-512" );
    md.update( inbytes );
    byte[] aMessageDigest = md.digest();

    String outEncoded = Base64.getEncoder().encodeToString( aMessageDigest );
    return( outEncoded );

Answer 4

You don't necessarily need the BouncyCastle library. The following code shows how to do so using the Integer.toHexString function

public static String sha256(String base) {
    try{
        MessageDigest digest = MessageDigest.getInstance("SHA-256");
        byte[] hash = digest.digest(base.getBytes("UTF-8"));
        StringBuffer hexString = new StringBuffer();

        for (int i = 0; i < hash.length; i++) {
            String hex = Integer.toHexString(0xff & hash[i]);
            if(hex.length() == 1) hexString.append('0');
            hexString.append(hex);
        }

        return hexString.toString();
    } catch(Exception ex){
       throw new RuntimeException(ex);
    }
}

Special thanks to user1452273 from this post: How to hash some string with sha256 in Java?

Keep up the good work !

Answer 5

return new String(Hex.encode(digest));

Answer 6

This is already implemented in the runtime libs.

public static String calc(InputStream is) {
    String output;
    int read;
    byte[] buffer = new byte[8192];

    try {
        MessageDigest digest = MessageDigest.getInstance("SHA-256");
        while ((read = is.read(buffer)) > 0) {
            digest.update(buffer, 0, read);
        }
        byte[] hash = digest.digest();
        BigInteger bigInt = new BigInteger(1, hash);
        output = bigInt.toString(16);
        while ( output.length() < 32 ) {
            output = "0"+output;
        }
    } 
    catch (Exception e) {
        e.printStackTrace(System.err);
        return null;
    }

    return output;
}

In a JEE6+ environment one could also use JAXB DataTypeConverter:

import javax.xml.bind.DatatypeConverter;

String hash = DatatypeConverter.printHexBinary( 
           MessageDigest.getInstance("MD5").digest("SOMESTRING".getBytes("UTF-8")));