Change AES to GCM/NoPadding mode

[QuickMythril]

https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Common_modes

• GCM can take full advantage of parallel processing and implementing GCM can make efficient use of an instruction pipeline or a hardware pipeline. The CBC mode of operation incurs pipeline stalls that hamper its efficiency and performance.
• CBC has been the most commonly used mode of operation. Its main drawbacks are that encryption is sequential (i.e., it cannot be parallelized), and that the message must be padded to a multiple of the cipher block size.

https://www.baeldung.com/java-aes-encryption-decryption

• The GCM has received significant attention and is recommended by NIST. The GCM model outputs ciphertext and an authentication tag. The main advantage of this mode, compared to other operation modes of the algorithm, is its efficiency.

https://isuruka.medium.com/selecting-the-best-aes-block-cipher-mode-aes-gcm-vs-aes-cbc-ee3ebae173c

• Both the AES-CBC and AES-GCM are able to secure your valuable data with a good implementation. but to prevent complex CBC attacks such as Chosen Plaintext Attack(CPA) and Chosen Ciphertext Attack(CCA) it is necessary to use Authenticated Encryption. So the best option is for that is GCM. AES-GCM is written in parallel which means throughput is significantly higher than AES-CBC by lowering encryption overheads.

https://helpdesk.privateinternetaccess.com/kb/articles/what-s-the-difference-between-aes-cbc-and-aes-gcm

• AES-GCM is a more secure cipher than AES-CBC, because AES-CBC, operates by XOR'ing (eXclusive OR) each block with the previous block and cannot be written in parallel. This affects performance due to the complex mathematics involved requiring serial encryption. AES-CBC also is vulnerable to padding oracle attacks, which exploit the tendency of block ciphers to add arbitrary values onto the end of the last block in a sequence in order to meet the specified block size.
• AES-GCM is written in parallel which means throughput is significantly higher than AES-CBC by lowering encryption overheads. Each block with AES-GCM can be encrypted independently. The AES-GCM mode of operation can actually be carried out in parallel both for encryption and decryption.

https://en.wikipedia.org/wiki/Padding_oracle_attack

• In symmetric cryptography, the padding oracle attack can be applied to the CBC mode of operation, where the "oracle" (usually a server) leaks data about whether the padding of an encrypted message is correct or not. Such data can allow attackers to decrypt (and sometimes encrypt) messages through the oracle using the oracle's key, without knowing the encryption key.

[crowetic]

This looks like a very well written proposal, and upon a quick glance, the code looks good to me as well. Thank you for this request. I will see if I can get a few others to look it over.

Seems like the backwards compatibility is there and all, so it should be good I think.