SEC: Switch to AES for encryption

[MartinThoma]

Currently, pypdf uses the security handler revision number 3 (R=3) and V=2. That means:

"Algorithm 1: Encryption of data using the RC4 or AES algorithms"
in 7.6.2, "General Encryption Algorithm," but permitting encryption key lengths
greater than 40 bits.

RC4 is not secure (source). At the very least we should issue a big warning + document this behavior. By default, we should use secure encryption methods

AES encryption is not implemented so far. Only decryption.

[xilopaint]

AES encryption is not implemented so far. Only decryption.

Is this mean pypdf can do AES decryption without external dependencies? If so, I thought even decryption would only be possible with PyCryptodome.

[MartinThoma]

even decryption would only be possible with PyCryptodome

That is correct