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/*
James Robson
Public domain.
*/
public class Curve25519Donna {
final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
public static String bytesToHex(byte[] bytes) {
char[] hexChars = new char[bytes.length * 2];
int v;
for ( int j = 0; j < bytes.length; j++ ) {
v = bytes[j] & 0xFF;
hexChars[j * 2] = hexArray[v >>> 4];
hexChars[j * 2 + 1] = hexArray[v & 0x0F];
}
return new String(hexChars);
}
public native byte[] curve25519Donna(byte[] a, byte[] b);
public native byte[] makePrivate(byte[] secret);
public native byte[] getPublic(byte[] privkey);
public native byte[] makeSharedSecret(byte[] privkey, byte[] theirPubKey);
public native void helowrld();
// Uncomment if your Java is 32-bit:
//static { System.loadLibrary("Curve25519Donna"); }
// Otherwise, load this 64-bit .jnilib:
static { System.loadLibrary("Curve25519Donna_64"); }
/*
To give the old tires a kick (OSX):
java -cp `pwd` Curve25519Donna
*/
public static void main (String[] args) {
Curve25519Donna c = new Curve25519Donna();
// These should be 32 bytes long
byte[] user1Secret = "abcdefghijklmnopqrstuvwxyz123456".getBytes();
byte[] user2Secret = "654321zyxwvutsrqponmlkjihgfedcba".getBytes();
// You can use the curve function directly...
//byte[] o = c.curve25519Donna(a, b);
//System.out.println("o = " + bytesToHex(o));
// ... but it's not really necessary. Just use the following
// convenience methods:
byte[] privKey = c.makePrivate(user1Secret);
byte[] pubKey = c.getPublic(privKey);
byte[] privKey2 = c.makePrivate(user2Secret);
byte[] pubKey2 = c.getPublic(privKey2);
System.out.println("'user1' privKey = " + bytesToHex(privKey));
System.out.println("'user1' pubKey = " + bytesToHex(pubKey));
System.out.println("===================================================");
System.out.println("'user2' privKey = " + bytesToHex(privKey2));
System.out.println("'user2' pubKey = " + bytesToHex(pubKey2));
System.out.println("===================================================");
byte[] ss1 = c.makeSharedSecret(privKey, pubKey2);
System.out.println("'user1' computes shared secret: " + bytesToHex(ss1));
byte[] ss2 = c.makeSharedSecret(privKey2, pubKey);
System.out.println("'user2' computes shared secret: " + bytesToHex(ss2));
}
}
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