How to write a hash function in Android similar to the Python function?

Question

I am currently developing a distributed system application. I want to verify a Python generated hash in the Android application. I have a python method to do hashing in given string variables.

This is the python function and it works well.

 hash_value = hashlib.sha1("PARAMETER123".encode("UTF-8")).hexdigest()

I want to implement the same function in my Android application. I hope some expert can help as soon as possible.

score 2 · Accepted Answer · edited May 23 '17 at 10:32

You can try the following code snippet,

String text = "PARAMETER123";

MessageDigest md = MessageDigest.getInstance("SHA-1");
byte[] textBytes = text.getBytes("UTF-8");
md.update(textBytes, 0, textBytes.length);
byte[] sha1hash = md.digest();

String encrypted_text = = convertToHex(sha1hash);

and the convertToHex() method

private static String convertToHex(byte[] data) {
        StringBuilder buf = new StringBuilder();
        for (byte b : data) {
            int halfbyte = (b >>> 4) & 0x0F;
            int two_halfs = 0;
            do {
                buf.append((0 <= halfbyte) && (halfbyte <= 9) ? (char) ('0' + halfbyte) : (char) ('a' + (halfbyte - 10)));
                halfbyte = b & 0x0F;
            } while (two_halfs++ < 1);
        }
        return buf.toString();
    }

This will convert a UTF-8 based text into a SHA1 hex.

Reference: https://stackoverflow.com/a/5980789/2506025

Thank You, I will comment after implementation. – uma Nov 02 '16 at 05:28 — uma, Nov 02 '16 at 05:28

score 2 · Answer 2 · answered Nov 02 '16 at 05:13

Here is a simple SHA1 method for Java:

String sha1Hash( String toHash )
{
    String hash = null;
    try
    {
        MessageDigest digest = MessageDigest.getInstance( "SHA-1" );
        byte[] bytes = toHash.getBytes("UTF-8");
        digest.update(bytes, 0, bytes.length);
        bytes = digest.digest();

        // This is ~55x faster than looping and String.formating()
        hash = bytesToHex( bytes );
    }
    catch( NoSuchAlgorithmException e )
    {
        e.printStackTrace();
    }
    catch( UnsupportedEncodingException e )
    {
        e.printStackTrace();
    }
    return hash;
}

// http://stackoverflow.com/questions/9655181/convert-from-byte-array-to-hex-string-in-java
final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
public static String bytesToHex( byte[] bytes )
{
    char[] hexChars = new char[ bytes.length * 2 ];
    for( int j = 0; j < bytes.length; j++ )
    {
        int v = bytes[ j ] & 0xFF;
        hexChars[ j * 2 ] = hexArray[ v >>> 4 ];
        hexChars[ j * 2 + 1 ] = hexArray[ v & 0x0F ];
    }
    return new String( hexChars );
}

You can include those methods and call sha1hash.

@Thank You, I will gave feed back after implementation . – uma Nov 02 '16 at 05:28 — uma, Nov 02 '16 at 05:28

How to write a hash function in Android similar to the Python function?

2 Answers2