Compute SHA-1 of byte array

Question

I\'m looking for a way of getting an SHA-1 checksum with a Java byte array as the message.

Should I use a third party tool or is there something built in to the JVM

Answer 1

This a snippet of code we use to convert to SHA-1 but takes a String instead of a Byte[] see this javadoc for further info

        import java.io.UnsupportedEncodingException;
        import java.security.MessageDigest;
        import java.security.NoSuchAlgorithmException;

        public class DoSHA1 {

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

            public static String SHA1(String text) throws NoSuchAlgorithmException,
UnsupportedEncodingException  {
            MessageDigest md = MessageDigest.getInstance("SHA-1");
            byte[] sha1hash = new byte[40];
            md.update(text.getBytes("iso-8859-1"), 0, text.length());
            sha1hash = md.digest();
            return convToHex(sha1hash);
            }
        }

Answer 2

You can do it yourself but I would recommend to use a library that has been proven to work, like Commons Codec. The class DigestUtils has several methods to calculate hashes.

Answer 3

...another option is to use Spring:

<bean id="passwordEncoder" class="org.springframework.security.authentication.encoding.ShaPasswordEncoder">
     <constructor-arg value="256"/>
 </bean>

read more here

HTH

Answer 4

I Just used this to compute the hash sum inside of a dex file and compare it with the value which is saved in the dex file.

i know this code hasnt very good style but its more PoC and only needed for some research which isnt time critical. may someone can use it!

class CheckDex{
public boolean checkSHA1(File f) throws IOException, NoSuchAlgorithmException{
    RandomAccessFile raf = new RandomAccessFile(f, "r");
    byte[] sig = new byte[20];
    raf.seek(0xC);
    for(int i = 0; i < 20; i++){
        sig[i] = (byte) raf.readUnsignedByte();
    }

    MessageDigest md = MessageDigest.getInstance("SHA-1"); 

    byte[] code = new byte[(int) (raf.length()-32)];
    for(int i = 0; i < code.length; i++){
        code[i] = (byte) raf.readUnsignedByte();
    }
    byte[] comsig = md.digest(code);

    raf.close();
    return Arrays.equals(sig,comsig);
}
}

Answer 5

What about:

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Formatter;

public static String SHAsum(byte[] convertme) throws NoSuchAlgorithmException{
    MessageDigest md = MessageDigest.getInstance("SHA-1"); 
    return byteArray2Hex(md.digest(convertme));
}

private static String byteArray2Hex(final byte[] hash) {
    Formatter formatter = new Formatter();
    for (byte b : hash) {
        formatter.format("%02x", b);
    }
    return formatter.toString();
}

Answer 6

From CommonCodec DigestUtils Implementation the Hex coversion after the Digest calculation as shown before :

MessageDigest md = MessageDigest.getInstance("SHA-1"); 
return byteArray2Hex(md.digest(convertme));

should be http://commons.apache.org/codec/apidocs/src-html/org/apache/commons/codec/binary/Hex.html#line.129 :

private static final char[] DIGITS_LOWER = 
   {'0', '1', '2', '3', '4', '5', '6', '7',
    '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};

private static final char[] DIGITS_UPPER = 
   {'0', '1', '2', '3', '4', '5', '6', '7',
    '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};

protected static char[] encodeHex(byte[] data, char[] toDigits) {
    int l = data.length;
    char[] out = new char[l << 1];
    // two characters form the hex value.
    for (int i = 0, j = 0; i < l; i++) {
        out[j++] = toDigits[(0xF0 & data[i]) >>> 4];
        out[j++] = toDigits[0x0F & data[i]];
    }
    return out;
}

protected static int toDigit(char ch, int index) throws DecoderException {
    int digit = Character.digit(ch, 16);
    if (digit == -1) {
        throw new DecoderException(
                    "Illegal hexadecimal character " 
            + ch + " at index " + index);
    }
    return digit;
}

public static String exampleSha1(String convertme){
    MessageDigest md = MessageDigest.getInstance("SHA-1"); 
    byte[] encodeHex = md.digest(convertme));
    return new String(encodeHex);
}