sweis

### Keybase proof

I hereby claim:

  * I am sweis on github.
  * I am sweis (https://keybase.io/sweis) on keybase.
  * I have a public key whose fingerprint is D4D2 0737 35F5 CB0F F6D9  BED1 9EF1 F36D 5B58 2B47

To claim this, I am signing this object:

sweis

//package ly.secret.android.net;

/**
 * This is source code derived from the Cryptfs class found in Secret.ly's android app.
 *
 * Comments and variable names are my own.
 *
 * Here's how I generated this file:
 * 1. Downloaded the Secret.ly APK via this link:
 *    http://storage.evozi.com/apk/dl/14/05/21/ly.secret.android.apk?vc=1600040

sweis

package p000;

import java.security.InvalidKeyException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;

import org.bouncycastle.crypto.InvalidCipherTextException;
import org.bouncycastle.jcajce.provider.asymmetric.p445ec.KeyAgreementSpi;

sweis

for (ExtractPublicKeysData publicKeysData : extractPublicKeysDataList) {
  Object userId = linkedHashMap.get(publicKeysData.registrationToken);

  KeyPairGeneratorSpi.EC ec = new KeyPairGeneratorSpi.EC();
  ec.initialize(SessionKeyEncrypter.secp256r1Spec());
  KeyPair ephemeralKeyPair = ec.generateKeyPair();

  PrivateKey ephemeralPrivateKey = ephemeralKeyPair.getPrivate();
  PublicKey recipientPublicKey = publicKeysData.identityKey.publicKey;
  byte[] sharedSecret =

sweis

// The IV seems to be the ephemeral public key of the sender and is the header of the encrypted 
// conversation key
byte[] ivMaybeEphemeralPublicKey = ArrayUtils.sliceCopy(0, encryptedConversationKey, 65);

int length = encryptedConversationKey.length - 65;
byte[] ciphertext = ArrayUtils.sliceCopy(65, encryptedConversationKey, length);

ECNamedCurveParameterSpec secp256r1Spec = SessionKeyEncrypter.secp256r1Spec();
ECPublicKeySpec spec = 
  new ECPublicKeySpec(secp256r1Spec.curve.decodePoint(ivMaybeEphemeralPublicKey), secp256r1Spec);