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 second example should be:

26 = 6 × 4 + 2
6 = 2 × 3 + 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.

In Section 2.5, on page 50, the second line marked “keyword 2” should end in “E E E”.

In Section 2.5, in the middle of page 51, it should say “So going back to our mystery ciphertext from page 46”.

In Section 2.7, near the bottom of page 57, it should say “tabula recta encryption”.

Figure 2.3 on page 59 was created by Wikipedia user “Matt Crypto”.

Figure 2.5 on page 60 was created by Eric Pierce, Wikipedia user name “Wapcaplet”.

Figure 2.6 on page 65 was created by Wikipedia user “RadioFan”.

In Section 2.8, in the example on page 65, the second-last line should be:

minus 1: 5 8 11 14 17 20 23 26 3 · · · 22 25 2

Figure 3.1 should be:

Figure 3.1. A scytale.

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.

In Sidebar 3.1, the ratio of the perimeter of a circle to its diameter should be 3.14159….

The caption for Table 5.1 should read “A series of ciphertexts encrypted with the same running key.”

At the beginning of Sidebar 5.1, on page 150, it should say “When you got to the part of this book about the contact method, in Section 3.7”.

In Sidebar 5.1, in the second paragraph on page 151, it should say “The chance of picking the letter a (for instance) out of the suspected plaintext is na / n“.

In the first paragraph of Section 5.3, on page 157, it should say “His idea was to use the plaintext itself as a “key” to construct the ciphertext”.

In Figure 5.2, the picture for “ECB encryption” should be:


Figure 5.15 should be:

Figure 5.15. The Trivium cipher.

In Sidebar 6.1, near the bottom of page 198, it should say “If n = paqbrc is a product containing three different primes”.

In Section 7.4, at the top of page 217, the first sentence of the paragraph should say “What the factoring problem was missing was a trap door”, and the end of the paragraph should say “the one-way function of multiplication would be the trap door in the one-way function of exponentiation.”

In Section 7.7, the chosen-ciphertext attack example on page 230 is incorrect.  The modulus n should be 4069, the encryption exponent e should be 749, and Eve’s “ciphertext” should be:

    “ciphertext”: 3029 1064 1402 3   5    1172 3917 1483
to the dth power: 1612 501  1905 243 3125 2008 114  1119
     “plaintext”: pl   ea   se   b?  ?y   th   an   ks

Also in Section 7.7,  at the bottom of page 231, it should say:

2214 ≡ P 3 modulo 3763      and      2019 ≡ P 17 modulo 3763.

In Appendix A, on page 239 (and also in the Index), Malcolm Williamson’s name is misspelled.

In Section 8.3, at the bottom of page 256, the last equation should be:

Also in Section 8.3, the second set of equations on page 257 should be:


Still in Section 8.3, on page 259, the second and third equations should be:

32 = 53 + 17


32 ≡ 53 + 17 modulo 7

In Section 8.5, on page 274, in the middle of the second paragraph, it should say:  “As the name suggests, Dual EC DRBG uses two elliptic curve discrete logarithm problems.”

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.”

In Section 9.2, on page 287, the first sentence of the first full paragraph should say “How do we make that into an asymmetric-key cryptographic system?”

Also in Section 9.2, on page 289, the letter t should correspond to the number 20 in four places.

In Section 9.3, near the bottom of page 293, it should say “Such a filter is designed to let photons through only if they are vibrating in the same direction as the filter.”

Figure 9.17 should be:

Figure 9.17. Polarized photons after passing through a filter.