I try to implement aes-128-cfb myself for learning. To confirm whether my implementation is correct, I want to verify it with a well-known library such as OpenSSL. But then I noticed something strange when I try to use OpenSSL to encrypt.
I have file
cleartext.txt with the following content:
This is cleartext that will be used to encrypt with OpenSSL.
Then I execute this command
openssl enc -aes-128-cfb -in cleartext.txt -K 48656c6c6f20576f726c642041455321 -iv 72616e646f6d20313662797465206976 -out output.txt
The strange thing is that the output file contains only 60 bytes. AES block is 16 bytes. The expected output size in byte should be multiple of 16. 60 is not multiple of 16.
Did I miss something important here?