cryptography - Android: CipherStream-API for AEAD Ciphers inacceptable slow

Question

We are having an android app which a decrypting and encrypting large (up to 100MB) files over HTTP-Streams.

Therefore, we are using CipherInputStreams and CipherOutputStreams which works fine for AES/CBC/PKCS7Padding. We recently switched to AES/GCM/NoPadding. Now the encryption and decryption is inacceptable slow for files over roughly 50MB.

Debugging into the android source code, reveals the issues: https://android.googlesource.com/platform/libcore/+/master/ojluni/src/main/java/javax/crypto/CipherInputStream.java#112

This method has byte buffer "oBuffer" which is reallocated and increased by 512bits until it can hold the whole message (see line: https://android.googlesource.com/platform/libcore/+/master/ojluni/src/main/java/javax/crypto/CipherInputStream.java#121)

I am aware of the note over this method which stated that in AEAD ciphers the whole message has to be buffered. This is one issue, because we cannot hold the whole message into a memory buffer. Another issue is that the oBuffer is constantly reallocated.

Is there any solution for using GCM with a streaming API?

Answer 1

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