Decoding AES with Base64 cyphertext and key I have a supposed AES cyphertext and key. 
They are both encoded in Base64 as they have trailing = for padding.

The key decodes down into 16 characters, so I am assuming its AES128.

I have tried to use the key and cyphertext to decode the message using 
the website “aesencryption.net” and OpenSSL with the following command: 

openssl enc -d -aes-128-ecb -base64 -in cypherText.txt -out /dev/stdout -pass pass:key


The online decoder gives me unreadable text, and OpenSSL produces a bad magic number. I have also tried a few of the other supported AES modes in OpenSSL with no luck.

Am I missing a crucial step?
Yes, it is AES. The ciphertext decrypts to

user: part4, password: 97531
{{{


PS: after some experiments I was able to decrypt it using the OpenSSL command line:

openssl enc -d -aes-128-ecb -in cipher.txt -out plain.txt -nopad -nosalt -K 10EABCFF45E05EBB7AF9A228DD31F216 -iv 0 -base64


I converted the key from base64 to hex first.