I found this on a forum post, and just wanted to verify that this information is correct:

for base64 the valid charset is:

ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwx yz0123456789+/

the = is used as filler for the last bytes, as the length must be mulitple

of 3(via thescripts.com/forum)

The charset looks reasonable, but must the length be a multiple of 3? (Seems like a multiple of 4 would make more sense.)

Comments very much appreciated!