Ethical hacking tutorials

'How is the Installation ID generated?'

To find an answer to this question, we trace back each digit of the
Installation ID to its origins.

>>> Check digits

The rightmost digit in each of the groups is a check digit to guard
against simple errors such as the call center agent's mistyping of one
of the digits read to him or her. The value of the check digit is
calculated by adding the other five digits in the group, adding the
digits at even positions a second time, and dividing the sum by
seven. The remainder of the division is the value of the check
digit. In the above example the check digit for the first group (6) is
calculated as follows.

1 | 2 | 3 | 4 | 5 <- position
---+---+---+---+---
0 | 0 | 2 | 6 | 6 <- digits

0 + 0 + 2 + 6 + 6 = 14 (step 1: add all digits)
0 + 6 + 14 = 20 (step 2: add even digits again)

step 3: division
20 / 7 = 2, remainder is 20 - (2 * 7) = 6


check digit is 6

Adding the even digits twice is probably intended to guard against the
relatively frequent error of accidentally swapping two digits while
typing, as in 00626 vs. 00266, which yield different check digits.

>>> Decoding

Removing the check digits results in a 41-digit decimal number. A
decimal number of this length roughly corresponds to a 136-bit binary
number. In fact, the 41-digit number is just the decimal encoding of
such a 136-bit multi-precision integer, which is stored in little
endian byte order as a byte array. Hence, the above Installation ID
can also be represented as a sequence of 17 bytes as in

0xXX 0xXX 0xXX 0xXX 0xXX 0xXX 0xXX 0xXX
0x94 0xAA 0x46 0xD6 0x0F 0xBD 0x2C 0xC8
0x00

In this representation of the above Installation ID 'X' characters
again substitute the digits that we prefer not to disclose. The '0x'
prefix denotes hex notation throughout this paper.