HMAC-SHA1

package amazon.webservices.common;

import java.security.SignatureException;
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

/**
* This class defines common routines for generating
* authentication signatures for AWS requests.
*/
public class Signature {
private static final String HMAC_SHA1_ALGORITHM = "HmacSHA1";


/**
* Computes RFC 2104-compliant HMAC signature.
* * @param data
* The data to be signed.
* @param key
* The signing key.
* @return
* The Base64-encoded RFC 2104-compliant HMAC signature.
* @throws
* java.security.SignatureException when signature generation fails
*/
public static String calculateRFC2104HMAC(String data, String key)
throws java.security.SignatureException
{
String result;
try {

// get an hmac_sha1 key from the raw key bytes
SecretKeySpec signingKey = new SecretKeySpec(key.getBytes(), HMAC_SHA1_ALGORITHM);

// get an hmac_sha1 Mac instance and initialize with the signing key
Mac mac = Mac.getInstance(HMAC_SHA1_ALGORITHM);
mac.init(signingKey);

// compute the hmac on input data bytes
byte[] rawHmac = mac.doFinal(data.getBytes());

// base64-encode the hmac
result = Encoding.EncodeBase64(rawHmac);

} catch (Exception e) {
throw new SignatureException("Failed to generate HMAC : " + e.getMessage());
}
return result;
}
}