1. Check Digit Scheme
Based on D5

2. Verhoeff's Check digit scheme
Catches all single digit errors
Catches all transposition errors involving adjacent digits
Uses only digits 0-9

3. Digital D5

4. How it works: Let = (0 1 5 8 9 4 2 7)(3 6)  is a permutation in S10
The check digit for 2935 is c, where
(2) 2( 9) 3(3) 4(5) 5(c) = 0
(multiplication is in digital D5)

5. Check digit for 2935 Recall = (0 1 5 8 9 4 2 7)(3 6)
Step 1: See page 112 for tables n 2935 –> 7*2*6*2*5(c) = 0
Now (7*2)*(6*2) = 5*9 = 1
So 5(c) = 1-1 = 4
Hence c = 0

6. Verify
29350 is legitimate
29450 is an error
29305 is an error