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Updated README

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Moxie Marlinspike 2015-02-03 10:20:08 -08:00
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# curve25519-java # curve25519-java
A Java Curve25519 implementation that is backed by native code when available, and 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 ## Installing
@ -23,35 +23,72 @@ To use from pure Java:
</dependency> </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 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. the Java artifact is a JAR that only contains the pure-Java Curve25519 provider.
## Using ## 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: ### Generating a Curve25519 keypair:
``` ```
SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG"); Curve25519KeyPair keyPair = Curve25519.getInstance(Curve25519.BEST).generateKeyPair();
Curve25519KeyPair keyPair = Curve25519.generateKeyPair(secureRandom);
``` ```
### Calculating a shared secret: ### 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: ### Calculating a signature:
``` ```
SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG"); Curve25519 cipher = Curve25519.getInstance(Curve25519.BEST);
byte[] signature = Curve25519.calculateSignature(secureRandom, privateKey, message); byte[] signature = cipher.calculateSignature(secureRandom, privateKey, message);
``` ```
### Verifying a signature: ### Verifying a signature:
``` ```
boolean validSignature = Curve25519.verifySignature(publicKey, message, signature); Curve25519 cipher = Curve25519.getInstance(Curve25519.BEST);
boolean validSignature = cipher.verifySignature(publicKey, message, signature);
``` ```
## License ## License