Updated README

README.md

@@ -1,7 +1,7 @@
 # curve25519-java
 
 A Java Curve25519 implementation that is backed by native code when available, and
-pure Java when a native library is not available.
+pure Java when a native library is not available. There is also a J2ME build variant.
 
 ## Installing
 
@@ -23,35 +23,72 @@ To use from pure Java:
 </dependency>
 ```
 
+To use from J2ME:
+
+```
+<dependency>
+  <groupId>org.whispersystems</groupId>
+  <artifactId>curve25519-j2me</artifactId>
+  <version>(latest version number here)</version>
+</dependency>
+```
+
+
 The Android artifact is an AAR that contains an NDK-backed native implementation, while
 the Java artifact is a JAR that only contains the pure-Java Curve25519 provider.
 
 ## Using
 
+## Obtaining an instance
+
+The caller needs to specify a `provider` when obtaining a Curve25519 instance.  There are
+four built in providers:
+
+1. `Curve25519.NATIVE` -- This is a JNI backed provider.
+1. `Curve25519.JAVA` -- This is a pure Java 7 backed provider.
+1. `Curve25519.J2ME` -- This is a J2ME compatible provider.
+1. `Curve25519.BEST` -- This is a provider that attempts to use `NATIVE`,
+   but falls back to `JAVA` if the former is unavailable.
+
+The caller specifies a provider during instance creation:
+
+```
+Curve25519 cipher = Curve25519.getInstance(Curve25519.BEST);
+```
+
+Since J2ME doesn't have built-in `SecureRandom` support, J2ME users need to supply their
+own source of `SecureRandom` by implementing the `SecureRandomProvider` interface and
+passing it in:
+
+```
+Curve25519 cipher = Curve25519.getInstance(Curve25519.J2ME, new MySecureRandomProvider());
+```
+
 ### Generating a Curve25519 keypair:
 
 ```
-SecureRandom      secureRandom = SecureRandom.getInstance("SHA1PRNG");
-Curve25519KeyPair keyPair      = Curve25519.generateKeyPair(secureRandom);
+Curve25519KeyPair keyPair = Curve25519.getInstance(Curve25519.BEST).generateKeyPair();
 ```
 
 ### Calculating a shared secret:
 
 ```
-byte[] sharedSecret = Curve25519.calculateAgreement(publicKey, privateKey);
+Curve25519 cipher       = Curve25519.getInstance(Curve25519.BEST);
+byte[]     sharedSecret = cipher.calculateAgreement(publicKey, privateKey);
 ```
 
 ### Calculating a signature:
 
 ```
-SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG");
-byte[]       signature    = Curve25519.calculateSignature(secureRandom, privateKey, message);
+Curve25519 cipher    = Curve25519.getInstance(Curve25519.BEST);
+byte[]     signature = cipher.calculateSignature(secureRandom, privateKey, message);
 ```
 
 ### Verifying a signature:
 
 ```
-boolean validSignature = Curve25519.verifySignature(publicKey, message, signature);
+Curve25519 cipher         = Curve25519.getInstance(Curve25519.BEST);
+boolean    validSignature = cipher.verifySignature(publicKey, message, signature);
 ```
 
 ## License