Convert base64 string to byte string

I already told you a few times, the documentation of that library is far from par.

Also @chrismcg told you to try Base.url_decode64!/1, which you obviously didn’t, as it works for me:

iex(1)> message = "Foo"
"Foo"
iex(2)> {:ok, key64} = ExCrypto.generate_aes_key(:aes_256, :base64)
{:ok, "YBFgCMzhnxIOVeirWf5hgzbFmUcvZcHY0yKRJJ4Ocks="}
iex(3)> key = Base.url_decode64!(key64)
<<96, 17, 96, 8, 204, 225, 159, 18, 14, 85, 232, 171, 89, 254, 97, 131, 54, 197,
  153, 71, 47, 101, 193, 216, 211, 34, 145, 36, 158, 14, 114, 75>>
iex(4)> {:ok, {iv, ciphered}} = ExCrypto.encrypt(key, message)
{:ok,
 {<<195, 207, 172, 38, 128, 248, 158, 10, 14, 239, 231, 195, 48, 154, 244, 177>>,
  <<4, 238, 11, 86, 7, 6, 5, 86, 13, 182, 189, 113, 193, 85, 194, 141>>}}
iex(5)> {:ok, clear} = ExCrypto.decrypt(key, iv, ciphered)
{:ok, "Foo"}

It seems as if you really need to actively read and understand the sources of this library to be able to use it.

My suggestion is, that you use :bytes with the key generator and then convert the resulting binary to exactly the format you really need. No surprises anymore because of bad documentation, that claims to return base64 encoded string but actually does return an Base64-URL-encoded string…

Mean I get an error:

(exit) an exception was raised:
** (MatchError) no match of right hand side value: {:error, “IV must be exactly 128 bits and key must be exactly 128, 192 or 256 bits”}

What do you mean by “did not answer”?

So I tested it before, but did not answer.

Looking at the source of the library it uses Base.url_encode64 so try Base.url_decode64!

No other solution?

Yes, but did not answer

Have you tried:

{:ok, {init_vec, cipher_text}} = ExCrypto.encrypt(Base.decode64!(aes_256_key), message)

?

My Problem is here. I need to have the key to be base64.

For use in ExCrypto.encrypt/2 you need to generate the key as :bytes.