fixed README.md

Author: tom zhou

README.md

@@ -1,7 +1,42 @@
-tweetnacl-java
-==============
+rewrite tweetnacl.c in pure Java
 
-Porting TweetNacl in Java
+
+### API/Usage
+
+#### Public key authenticated encryption
+
+* get key pair: Box.KeyPair kp = Box.keyPair(), kp = Box.keyPair_fromSecretKey(sk)
+* new Box object: Box box = new Box(theirPublicKey, mySecretKey, Nonce);
+* encryption: cipher = box.box(message);
+* decryption: message = box.open(cipher);
+* Nonce MUST be unique for ever message passed between same peers
+
+
+#### Secret key authenticated encryption
+
+* get shared key: crypto random, what you have
+* new SecretBox object: SecretBox sbox = new SecretBox(sharedKey, Nonce);
+* encryption: cipher = sbox.box(message);
+* decryption: message = sbox.open(cipher);
+* Nonce MUST be unique for ever message passed between same peers
+
+
+### Signature
+
+* get key pair: Signature.KeyPair kp = Signature.keyPair(), kp = Signature.keyPair_fromSecretKey(sk);
+* new Signature object: Signature sig = new Signature(theirPublicKey, mySecretKey);
+* sign: signedMessage = sig.sign(message);
+* verify: message = sig.open(signedMessage);
+* Nonce MUST be unique for ever message passed between same peers
+
+
+### Hash
+
+* generate SHA-512: byte [] tag = Hash.sha512(message);
+
+
+### Refer to com.iwebpp.crypto.tests for details
 
 
 ### License MIT
+