Settle on/be clearer and more consistent about not-thread-safety

src/main/java/com/eatthepath/noise/NoiseHandshake.java

@@ -32,6 +32,8 @@
  * type (i.e. one-way or interactive) and pass Noise transport messages between the initiator and responder as
  * needed.</p>
  *
+ * <p>Noise handshake instances are stateful and are <em>not</em> thread-safe.</p>
+ *
  * <h2>Interactive patterns</h2>
  *
  * <p>In the most common case, Noise handshakes implement a interactive pattern in which both parties will send and

src/main/java/com/eatthepath/noise/NoiseTransport.java

@@ -1,9 +1,11 @@
 package com.eatthepath.noise;
 
 /**
- * A Noise transport is an interactive reader and writer of Noise transport messages. In the terminology of the Noise
+ * <p>A Noise transport is an interactive reader and writer of Noise transport messages. In the terminology of the Noise
  * Protocol Framework specification, a {@code NoiseTransport} instance encapsulates the two "cipher states" produced by
- * "splitting" a {@link NoiseHandshake}.
+ * "splitting" a {@link NoiseHandshake}.</p>
+ *
+ * <p>Noise transport instances are stateful and are <em>not</em> thread-safe.</p>
  *
  * @see NoiseHandshake#toTransport()
  */

src/main/java/com/eatthepath/noise/NoiseTransportReader.java

@@ -5,9 +5,11 @@
 import java.nio.ByteBuffer;
 
 /**
- * A Noise transport reader decrypts Noise transport messages. In the terminology of the Noise
+ * <p>A Noise transport reader decrypts Noise transport messages. In the terminology of the Noise
  * Protocol Framework specification, a {@code NoiseTransportReader} instance encapsulates a "cipher state" produced by
- * "splitting" a {@link NoiseHandshake} instance.
+ * "splitting" a {@link NoiseHandshake} instance.</p>
+ *
+ * <p>Noise transport reader instances are stateful and are <em>not</em> thread-safe.</p>
  *
  * @see NoiseHandshake#toTransportReader()
  * @see NoiseHandshake#toTransport()

src/main/java/com/eatthepath/noise/NoiseTransportWriter.java

@@ -4,9 +4,11 @@
 import java.nio.ByteBuffer;
 
 /**
- * A Noise transport writer encrypts Noise transport messages. In the terminology of the Noise Protocol Framework
+ * <p>A Noise transport writer encrypts Noise transport messages. In the terminology of the Noise Protocol Framework
  * specification, a {@code NoiseTransportWriter} instance encapsulates a "cipher state" produced by "splitting" a
- * {@link NoiseHandshake} instance.
+ * {@link NoiseHandshake} instance.</p>
+ *
+ * <p>Noise transport writer instances are stateful and are <em>not</em> thread-safe.</p>
  *
  * @see NoiseHandshake#toTransportWriter()
  * @see NoiseHandshake#toTransport()

src/main/java/com/eatthepath/noise/component/AbstractNoiseCipher.java

@@ -1,24 +1,26 @@
 package com.eatthepath.noise.component;
 
 import javax.annotation.Nullable;
-import javax.annotation.concurrent.ThreadSafe;
 import javax.crypto.*;
 import java.nio.ByteBuffer;
 import java.security.InvalidAlgorithmParameterException;
 import java.security.InvalidKeyException;
 import java.security.Key;
 import java.security.spec.AlgorithmParameterSpec;
 
-@ThreadSafe
 abstract class AbstractNoiseCipher implements NoiseCipher {
 
+  private final Cipher cipher;
+
+  AbstractNoiseCipher(final Cipher cipher) {
+    this.cipher = cipher;
+  }
+
   @FunctionalInterface
   private interface CipherFinalizer<T> {
     T doFinal() throws IllegalBlockSizeException, BadPaddingException, ShortBufferException;
   }
 
-  protected abstract Cipher getCipher();
-
   protected abstract AlgorithmParameterSpec getAlgorithmParameters(final long nonce);
 
   @Override
@@ -28,8 +30,6 @@ public int encrypt(final Key key,
                      final ByteBuffer plaintext,
                      final ByteBuffer ciphertext) throws ShortBufferException {
 
-    final Cipher cipher = getCipher();
-
     initCipher(cipher, Cipher.ENCRYPT_MODE, key, nonce);
 
     if (associatedData != null) {
@@ -54,8 +54,6 @@ public int encrypt(final Key key,
                      final byte[] ciphertext,
                      final int ciphertextOffset) throws ShortBufferException {
 
-    final Cipher cipher = getCipher();
-
     initCipher(cipher, Cipher.ENCRYPT_MODE, key, nonce);
 
     if (associatedData != null) {
@@ -73,8 +71,6 @@ public int decrypt(final Key key,
                      final ByteBuffer ciphertext,
                      final ByteBuffer plaintext) throws AEADBadTagException, ShortBufferException {
 
-    final Cipher cipher = getCipher();
-
     initCipher(cipher, Cipher.DECRYPT_MODE, key, nonce);
 
     if (associatedData != null) {
@@ -99,8 +95,6 @@ public int decrypt(final Key key,
                      final byte[] plaintext,
                      final int plaintextOffset) throws AEADBadTagException, ShortBufferException {
 
-    final Cipher cipher = getCipher();
-
     initCipher(cipher, Cipher.DECRYPT_MODE, key, nonce);
 
     if (associatedData != null) {

src/main/java/com/eatthepath/noise/component/AesGcmCipher.java

@@ -1,6 +1,5 @@
 package com.eatthepath.noise.component;
 
-import javax.annotation.concurrent.ThreadSafe;
 import javax.crypto.Cipher;
 import javax.crypto.NoSuchPaddingException;
 import javax.crypto.spec.GCMParameterSpec;
@@ -10,11 +9,13 @@
 import java.security.NoSuchAlgorithmException;
 import java.security.spec.AlgorithmParameterSpec;
 
-@ThreadSafe
 class AesGcmCipher extends AbstractNoiseCipher {
 
-  @Override
-  protected Cipher getCipher() {
+  AesGcmCipher() {
+    super(getCipher());
+  }
+
+  private static Cipher getCipher() {
     try {
       return Cipher.getInstance("AES/GCM/NoPadding");
     } catch (final NoSuchAlgorithmException | NoSuchPaddingException e) {

src/main/java/com/eatthepath/noise/component/ChaCha20Poly1305Cipher.java

@@ -1,6 +1,5 @@
 package com.eatthepath.noise.component;
 
-import javax.annotation.concurrent.ThreadSafe;
 import javax.crypto.Cipher;
 import javax.crypto.NoSuchPaddingException;
 import javax.crypto.spec.IvParameterSpec;
@@ -11,23 +10,15 @@
 import java.security.NoSuchAlgorithmException;
 import java.security.spec.AlgorithmParameterSpec;
 
-@ThreadSafe
 class ChaCha20Poly1305Cipher extends AbstractNoiseCipher {
 
   private static final String ALGORITHM = "ChaCha20-Poly1305";
 
   public ChaCha20Poly1305Cipher() throws NoSuchAlgorithmException {
-    // Make sure that we can instantiate a cipher and fail fast if not
-    try {
-      Cipher.getInstance(ALGORITHM);
-    } catch (final NoSuchPaddingException e) {
-      // This should never happen since we're not specifying a padding
-      throw new AssertionError("Padding not supported, but no padding specified", e);
-    }
+    super(getCipher());
   }
 
-  @Override
-  protected Cipher getCipher() {
+  private static Cipher getCipher() {
     try {
       return Cipher.getInstance(ALGORITHM);
     } catch (final NoSuchPaddingException e) {

src/main/java/com/eatthepath/noise/component/NoiseCipher.java

@@ -1,22 +1,17 @@
 package com.eatthepath.noise.component;
 
 import javax.annotation.Nullable;
-import javax.annotation.concurrent.ThreadSafe;
 import javax.crypto.AEADBadTagException;
 import javax.crypto.ShortBufferException;
 import java.nio.ByteBuffer;
 import java.security.Key;
 import java.security.NoSuchAlgorithmException;
 
 /**
- * <p>A Noise cipher is a stateless object that encrypts and decrypts data for use in a Noise protocol. Noise cipher
- * implementations must be thread-safe (i.e. calling encryption/decryption methods on different sets of data
- * concurrently and from different threads must have no adverse effect).</p>
- *
- * <p>Noise cipher implementations must operate in AEAD mode, produce a 16-byte AEAD tag when encrypting data, and
- * verify a 16-byte AEAD tag when decrypting data.</p>
+ * A Noise cipher is a stateless object that encrypts and decrypts data for use in a Noise protocol. Noise cipher
+ * implementations must operate in AEAD mode, produce a 16-byte AEAD tag when encrypting data, and verify a 16-byte
+ * AEAD tag when decrypting data.
  */
-@ThreadSafe
 public interface NoiseCipher {
 
   /**