For instance, the following 15 bytes were used to generate an HTTP parameter during our analysis:    Random Value Constant Value agent_id   0F EE C8 83 56 0E 9F F0 EB 98 43 30 30 30 30    The resulting ciphertext is then encoded using XAgent’s base64 encoding routine that starts by building the following encoding alphabet: ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_ As you can see, this is not the standard base64 alphabet, rather it is the “URL and Filename safe” Base 64 Alphabet from RFC 4648, as the “+” in the standard alphabet is replaced with “-” and the “/” replaced with “_”