//[[restapi:start|RESTful API]]//

====== Ciphering Data ======

Sometimes using this REST API we find ourselves in situations where we need to use some kind of encryption in order to //pass through some text// parameters that could contain special characters and may cause data loss or maybe to //obfuscate text// to make it more secure

To avoid this kind of situations we use use Base64 or SHA256.

All classes used here are present in [[http://www.oracle.com/technetwork/java/javase/downloads/index.html|Java 1.8]]. //No additional libraries are required//

===== Base64 - Encode =====

We can easily transform a text block into a Base64 String in java by doing

<code java>
new String(Base64.getUrlEncoder().encode(data), StandardCharsets.UTF_8);
</code>

===== Base64 - Decode =====

Also, we can decode a Base64 String into regular text by doing:

<code java>
new String(Base64.getUrlDecoder().decode(data.getBytes(StandardCharsets.UTF_8)), StandardCharsets.UTF_8);
</code>

===== SHA256 - Cipher =====

In java it's pretty easy to cipher using SHA256, the following method uses no libraries to achieve that goal

<code java>
private static String signHmacSHA256(String message, byte[] key) {
	try {
		SecretKey signingKey = new SecretKeySpec(key, "HMACSHA256");
		Mac mac = Mac.getInstance("HMACSHA256");
		mac.init(signingKey);
		byte[] digest = mac.doFinal(message.getBytes("UTF-8"));
		char[] hexadecimals = new char[digest.length * 2];
		for (int i = 0; i < digest.length; ++i) {
			for (int j = 0; j < 2; ++j) {
				int value = (digest[i] >> (4 - 4 * j)) & 0xf;
				char base = (value < 10) ? ('0') : ('a' - 10);
				hexadecimals[i * 2 + j] = (char) (base + value);
			}
		}
		return new String(hexadecimals);
	} catch (Exception e) {
		e.printStackTrace();
		return message;
	}
}
</code>

===== HmacSHA512 - Cipher =====

In java it's possible to cipher using HmacSHA512, the following method uses the following libraries to achieve that goal

<code java>
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import javax.xml.bind.DatatypeConverter;
</code>

An example

<code java>
private String sign(String algorithm, String input, byte[] key) throws Exception {
	    Mac mac = Mac.getInstance(algorithm);
	    mac.init(new SecretKeySpec(key, algorithm));
	    return DatatypeConverter.printHexBinary(mac.doFinal(input.getBytes("UTF-8"))).toLowerCase();
	}
</code>