Async MAC authentication for HTTP range requests. Fixes #38

main/crypto-api/src/main/java/org/cryptomator/crypto/Cryptor.java

@@ -75,6 +75,11 @@ public interface Cryptor extends SensitiveDataSwipeListener {
 	 */
 	Long decryptedContentLength(SeekableByteChannel encryptedFile) throws IOException;
 
+	/**
+	 * @return true, if the stored MAC matches the calculated one.
+	 */
+	boolean isAuthentic(SeekableByteChannel encryptedFile) throws IOException;
+
 	/**
 	 * @return Number of decrypted bytes. This might not be equal to the encrypted file size due to optional metadata written to it.
 	 * @throws DecryptFailedException If decryption failed

main/crypto-api/src/main/java/org/cryptomator/crypto/SamplingDecorator.java

@@ -81,6 +81,11 @@ public class SamplingDecorator implements Cryptor, CryptorIOSampling {
 		return cryptor.decryptedContentLength(encryptedFile);
 	}
 
+	@Override
+	public boolean isAuthentic(SeekableByteChannel encryptedFile) throws IOException {
+		return cryptor.isAuthentic(encryptedFile);
+	}
+
 	@Override
 	public Long decryptFile(SeekableByteChannel encryptedFile, OutputStream plaintextFile) throws IOException, DecryptFailedException {
 		final OutputStream countingInputStream = new CountingOutputStream(decryptedBytes, plaintextFile);