title: Encrypting with AES-256 and PKCS7 padding
body: <p>I want to use python to encrypt some data and have come across pycrypto as a possible tool.  In order to encrypt the data, I need to:</p>
  
  <ol>
  <li>Input passphrase string</li>
  <li>SHA-256 the string, giving key for AES-256</li>
  <li>Represent sensitive data as string of 9 digit characters (ascii), with leading ascii 0s if present (the data will always be in this format).</li>
  <li>Encrypt data string using AES-256, NO SALT, using PKCS7 padding from RFC2315, in ecb mode. </li>
  <li>Represent ciphertext as Base64 (RFC 4648), needing 24 characters</li>
  </ol>
  
  <p>Using pycrypto, steps 1-3 are fairly easy.  4 is giving me a little bit of trouble.  I'm not sure what PKCS7 padding is, and I am not sure how to ensure that the encryption is not using a SALT.  I was hoping someone could point me in the right direction re: step 4. </p>