OpenSSL: Bad magic number using command line tool
<p>For background, I am working through the <a href="https://cryptopals.com/" rel="nofollow">Matasano Crypto Challenges</a>. One of the problems (Set1, Challenge 7) is to decrypt an AES-128 ECB mode <a href="https://cryptopals.com/static/challenge-data/7.txt" rel="nofollow">file</a> with a given key, YELLOW SUBMARINE.</p>

<p>The file is base64 encoded and I can decrypt the file in Python but I cannot using the Windows 10 <code>openssl</code> command line tool.</p>

<p>The command I am running is:</p>

<p><code>openssl aes-128-ecb -d -a -in 7.txt -pass pass:"YELLOW SUBMARINE"</code></p>

<p>When I run this I am told that I have a <code>bad magic number</code>.</p>

<p>Does anyone have an idea of why I am getting this error?</p>