NODE 3f48c047No Subject
owner-cypherpunks@toad.comFri, 23 Feb 1996 02:27:00 +0800
> > Is there something like a checksum attached to Credit Card
> > Numbers. Or better: Is there a way to determine for a given
> > number N if
> > -this _might_ be a valid number
> > -this can't be a valid number
This was posted by Wayne D. Hoxsie Jr. <hoxsiew@crl.com>:
#include <stdio.h>
v(char *s)
{
int i=0,j=0,k;
k=!(!s[16]);
for(;*s;*s++)
i+=(++j%2-k)?(*s-'0')*2>9?((*s-'0')*2)-9:(*s-'0')*2:*s-'0';
return (i%10);
}
main()
{
char s[160];
printf("Enter credit card number\n");
scanf("%s",s);
printf("Credit card number is %svalid\n",v(s)?"in":"");
}
---
Dr. Dimitri Vulis
Brighton Beach Boardwalk BBS, Forest Hills, N.Y.: +1-718-261-2013, 14.4Kbps