In Section 1.3, in the middle of page 7, it should say “Well,

we should translate our letters into numbers, of course.”

Also, in Section 1.3, on page 13, the third example should be:

26 = 3 × 8 + 2

3 = 1 × 2 + 1

2 = 2 × 1 + 0

In Section 1.7, on page 26, we find that the example does not work as stated because (5 × 24 − 22 × 5) does not have an inverse modulo 26. If Eve was in this position she would have to try again with a different pair of plaintext blocks. For example, if she used the first and last block she would find (10 × 24 − 1 × 5) does have an inverse, so she could finish the attack.

Figure 2.3 was created by Wikipedia user “Matt Crypto”.

Figure 2.5 was created by Eric Pierce, Wikipedia user name “Wapcaplet”.

Figure 2.6 was created by Wikipedia user “RadioFan”.

In Section 3.3, at the bottom of page 84, there are two ! symbols missing. It should say:

Mathematicians use the symbol* n*! to represent this number and call it the factorial of *n*, or just *n* factorial. Factorials get pretty big pretty fast; for example 12! = 479,001,600, so there are 479,001,600 different permutation ciphers using 12-letter groups.

The caption for Figure 9.13 should read: “A good set of generators (top) and a bad set of generators (bottom) for the same lattice.”

Figure 9.17 should be:

Figure 9.17. Polarized photons after passing through a filter.