When using openssl or libressl to encrypt or decrypt data with AES, I typically specify -iter 1000000 -pbkdf2 to explicity force the key derivation method.
However I'm currently dealing with a remote system that has an older openssl version (openssl version says OpenSSL 1.0.2k-fips 26 Jan 2017) and it doesn't support the -iter or -pbkdf2 parameters.
If I encrypt a plaintext file on the old machine like this:
openssl enc -aes-256-cbc -salt -md sha512 -pass file:MySecretKey -in plain.txt -out cipher.bin
I can decrypt the result on newer systems like so:
libressl enc -d -aes-256-cbc -md sha512 -pass file:MySecretKey -in cipher.bin
The latter gives me a warning though:
*** WARNING : deprecated key derivation used.
Using -iter or -pbkdf2 would be better.
However it does output the correct plaintext result.
I'm wondering, if not PBKDF2, what kind of key derivation method is used by the old openssl?
