Thanks for all the input 
Though we decided against aes just now, I came up with the following solution to the mysql implementation of aes_ecb as a personal challenge, which works well in my test cases:
#
# Encrypt password with 128-bit aes and insert into database as hex value
#
@aes_blocksize 16
def encrypt(data, key) do
:crypto.block_encrypt(
:aes_ecb,
mysql_key_pad(key),
pkcs7_pad(data, @aes_block_size)
)
|> Base.encode16()
end
# PKCS7 Padding
defp pkcs7_pad(data, blocksize) do
pad = blocksize - rem(byte_size(data), blocksize)
data <> to_string(List.duplicate(pad, pad))
end
defp mysql_key_pad(key) when byte_size(key) < @aes_block_size do
bits = 8 * (@aes_block_size - byte_size(key))
key <> <<0 :: size(bits)>>
end
defp mysql_key_pad(key) when byte_size(key) == @aes_block_size do
key |> :binary.bin_to_list()
end
defp mysql_key_pad (key) do
bytelist = :binary.bin_to_list(key)
bytes_to_pad = (@aes_block_size - rem(length(bytelist), @aes_block_size))
bytelist ++ List.duplicate(<<0::8>>, bytes_to_pad)
|> Enum.chunk_every(@aes_block_size)
|> Enum.reduce(
List.duplicate(<<0::8>>, @aes_block_size),
fn chunk, acc ->
:crypto.exor(acc, chunk)
end
)
end
You can also implement the functionality of :crypto.exor(acc, chunk) in Elixir with a recursive function like
do_xor_calculation(chunk1, chunk2, accumulator), as I did first, but with :crypto.exor/2 it is way more comfortable.
