Vigenere Cipher - Decryption (Unknown Key)

This video shows the process (thoroughly) of how to find the key when you don't have it. English alphabet frequencies: http://www.math.cornell.edu/~mec/2003-2004/cryptography/subs/frequencies.html Decryption (known key): http://youtu.be/oHcJ4QLiiP8 Encryption: http://youtu.be/izFivfLjD5E