# Datanet Resources

Material related to the lectures on network security.

## Slides

### Reference:

Most Wikipedia articles on network security related topics are as good or better and more current than the treatment in the textbook Computer Networking.

### Textbooks:

• Bruce Schneier: Applied Cryptography. Serious introduction to most things cryptography with good explanations (algorithms, protocols, implementations).
• Ross Anderson: Security Engineering. How security is implemented in the real world and what problems and threats systems must solve and resist.
• Alfred Menezes et. al: Handbook of Applied Cryptography. Full covering of most areas of crypto, contrary to the title, this is a theory book. All chapters are available for free download as pdf-files

## Error in RSA proof in Computer Networking

In the fourth edition it's on page 696.

There is correct proofs for RSA on Wikipedia: http://en.wikipedia.org/wiki/Rsa and in Handbook of Applied Cryptography, Section 8.2.1.

```From: Christian Boesgaard [mailto:pink@diku.dk]
Sent: Wednesday, October 11, 2006 3:46 PM
To: ross@poly.edu
Subject: errata for Computer Networking, third edition

I think your proof for RSA on page 669 is wrong as you use a result
that does not cover all cases. You use the result:

If p and q are primes and n=pq, then

x^y mod n  ==  x^( y mod ((p-1) (q-1)) ) mod n

But this does not hold in general, for example the case where x=2,
y=4, p=3, q=3:

2^4 mod 9 = 7, but

2^(4 mod (2 * 2)) mod 9 = 1

So the RSA proof does not hold in general.

I think the result you want is the following corrolar to Eulers theorem:

If p and q are primes and n=pq, then

x^(1 mod ((p-1) (q-1))) mod n  ==  x mod n
```