Are there any possible simple methods/ways to generate/encrypt a 16 digit alpha-number into a 6 to 8 digit alpha-numeric code. There will be millions of possible combinations of the 16 digit number, so the encrypted 6-8 alpha-numeric number has to be unique. Thanks for your suggestions in advance.
Let's do the math, it only hurts for a moment:
16 digits: 0-9 is 10 characters
10^16 = 10,000,000,000,000,000
alpha-numeric with 0-9a-zA-Z is 62 characters
62^8 = 53,459,728,531,456
Since 10,000,000,000,000,000
is greater than
53,459,728,531,456
then no.
But if you are willing to use a larger character set including accented characters, foriegn characters and perhaps emoji then yes.
If you use a character set with 100 characters
100^8 = 10^16
then yes.
If you use a character set with 465 characters
465^6 ~= 10.1^16
then yes.