is there any logic or reason for the the change in numbers on a replacement debit card?

[joko]

i mean the last 4 digits change with each new card you have - but is this a random selection - or is there soem process to determine what these would be?

and if so could the new number be guessed based on the old one?

just wondered if i needed to shred my old receipts too ( i always do anyway)

thanks

[Mr Veritas]

I would imagine that it HAS to be random for security purposes.