Generate unique random numbers in Postgresql with fixed length

I need to generate unique random numbers in Postgresql with a fixed length of 13 digits. I've found a similar thread where was used a sequence encrypted using "pseudo_encrypt", but the returned number was not with a fixed length.

So, what i need is: get an encrypted random sequence with a fixed length of 13 digits where the min value is 0000000000001 and a max value is 9999999999999.

Is it possible? If start with the zeros in front is not possible is not a big problem (i think), i can set them programmatically during the reading from the db, but would be great if Postgresql can do it by itself.