From the aescrypt README.html:

   This is a program for encrypting/decrypting streams of data using
   Rijndael and Cipher Block Feedback mode (CFB-128).

   ...

   5. This program was deliberately kept extremely simple. It is not
      intended to be a full encryption solution, it is intended to be
      used within scripts as part of a complete solution. Keychain
      management, public key signatures, etc. are all expected to be
      done external to this program.