Moved stream crypto to crypto component.

briar-api/src/org/briarproject/api/crypto/StreamDecrypter.java

@@ -0,0 +1,14 @@
+package org.briarproject.api.crypto;
+
+import java.io.IOException;
+
+public interface StreamDecrypter {
+
+	/**
+	 * Reads a frame, decrypts its payload into the given buffer and returns
+	 * the payload length, or -1 if no more frames can be read from the stream.
+	 * @throws java.io.IOException if an error occurs while reading the frame,
+	 * or if authenticated decryption fails.
+	 */
+	int readFrame(byte[] payload) throws IOException;
+}