How to generate HMAC-SHA1 Signature in android?

Question

This is my base String:

        String args ="oauth_consumer_key="+enc(consumerkey) +
                   "&oauth_nonce="+enc(generateNonce()) +
                   "&oauth_signature_method=HMAC-SHA1" +
                   "&oauth_timestamp="+ timestamp +
                   "&oauth_token="+enc(Home.consToken) +
                   "&oauth_verifier="+verifier+"&oauth_version=1.0";
                    String base ="POST&"+enc("https://api.linkedin.com/uas/oauth   /accessToken") +"&"+ enc(args);

       String signature =computeHmac(base,consumer_secret+"&"+secretToken);

This is my Header:

        String header = "OAuth " +
       "oauth_consumer_key=\""+ enc(consumerkey)+ "\"," +
       "oauth_nonce=\""+ enc(generateNonce()) + "\"," +
       "oauth_signature_method=\"HMAC-SHA1\"," +
       "oauth_timestamp=\""+ timestamp + "\"," +
       "oauth_token=\""+Home.consToken + "\"," +
       "oauth_signature=\""+enc(signature)+"\","+
       "oauth_verifier=\""+verifier +"\","+ 
       "oauth_version=\""+1.0+"\"" ;

I am using following method to generate Signature:

public String computeHmac(String baseString, String key)
    throws NoSuchAlgorithmException, InvalidKeyException, IllegalStateException,  UnsupportedEncodingException
{
    Mac mac = Mac.getInstance("HmacSHA1");
    SecretKeySpec secret = new SecretKeySpec(key.getBytes(), mac.getAlgorithm());
    mac.init(secret);
    byte[] digest = mac.doFinal(baseString.getBytes());
    byte[] result=Base64.encodeBase64(digest);
    return new String(result);
}

while executing this code i am getting the following error...

oauth_problem=signature_invalid&    
oauth_problem_advice=com.linkedin.security.auth.pub.LoginDeniedInvalidAuthTokenException

can anybody help me out this?

Thanks...

Answer 1

Femi's answer is absolutely correct, however, it wasn't obvious for me what exactly is intval(b). As i understood it's b & 0xFF.

Also I applied some optimizations (that I found here) and here is my code:

private static String hmacSha1(String value, String key)
        throws UnsupportedEncodingException, NoSuchAlgorithmException,
        InvalidKeyException {
    String type = "HmacSHA1";
    SecretKeySpec secret = new SecretKeySpec(key.getBytes(), type);
    Mac mac = Mac.getInstance(type);
    mac.init(secret);
    byte[] bytes = mac.doFinal(value.getBytes());
    return bytesToHex(bytes);
}

private final static char[] hexArray = "0123456789abcdef".toCharArray();

private static String bytesToHex(byte[] bytes) {
    char[] hexChars = new char[bytes.length * 2];
    int v;
    for (int j = 0; j < bytes.length; j++) {
        v = bytes[j] & 0xFF;
        hexChars[j * 2] = hexArray[v >>> 4];
        hexChars[j * 2 + 1] = hexArray[v & 0x0F];
    }
    return new String(hexChars);
}