About

Pages on Security is an educational blog about information security.

I have initially created the content for the courses I teach at the University of Bucharest (BSc and MSc levels).  Thus, I had previously used, and I will continue to use Pages on Security as teaching material for my students. 

The initial idea was to give my students a single "page" on a specific topic and discuss it, encouraging active learning in class. So, each post contains one such "page" to which I add a (brief) explanation. 

Pages on Security uses a color code:

  • Concepts, Notions, … 
  • Constructions, Examples, … 
  • Attacks, Weaknesses, …

I have decided to make Pages on Security publicly available and not try to publish it as a course book. I hope it will become valuable material for students (worldwide) but also for others that are interested in the topic. 

Let me know if you are an educator who uses Pages on Security as a resource in class, or if Pages on Security helped you in any way as a student or professional. 

Help me improve the content by adding constructive comments to the posts. Alternatively, you can also contact me directly - check my personal webpage.

Ruxandra

Popular posts from this blog

Principles

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  There exist many  principles  in information security. By  principle  I understand some general guidelines or best practices one should be aware of and apply when designing/implementing/configuring/etc. secure systems (You might sometimes find sources that refer to the components of the  CIA Triad  - see Crypt(?)   -  as principles; that is not what this post is about). I also use the term  principle  to follow the first in line:  Kerckhoff's principle, which is  maybe the most known principle in cryptology.  The list is not exhaustive, but I think it is a good selection. Also, keep in mind that implementing one principle depends on the situation (goal, costs, trade-off with other aspects such as efficiency and usability, etc.). Kerckhoffs's principle is the second in a list of six principles specified by A.Kerckhoffs in his paper entitled La Cryptographie Militaire , published in 1883 [1]. The article is ...
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Perfect Secrecy and the One Time Pad (OTP)

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I have explained unconditional  (or  information-theoretical)  security in my previous post (see Unconditional vs. Conditional Security ). As I have mentioned there, we can refer to unconditional security in the context of various cryptographic primitives, among which the  encryption schemes (see Symmetric vs. Asymmetric Encryption ). An encryption scheme that is information-theoretically secure provides  perfect secrecy (see, e.g., [1]) ,  because the  ciphertext  perfectly  hides  the  plaintext.  In other words, the adversary has the same probability to correctly indicate the message  m  regardless if he/she knows the corresponding ciphertext  c.  Hence, the knowledge of the ciphertext gives no new information about the plaintext. We ignore the length of the message - which, of course, is exposed - and assume that all the possible messages are equally long. More rigorously, the  a-posteriori ...
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Cryptographic Hash Functions

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  The cryptographic hash functions are well-known cryptographic primitives. They are widely used, either as stand-alone or as a building block in other, more complex constructions. Their applicability covers a wide area, some popular examples being password storage, electronic signatures, and blockchain. Please note that cryptographic hash functions must satisfy some (of the) security notions I will discuss later on, while non-cryptographic hash functions do not necessarily have to. Therefore, not all hash functions are cryptographically strong. Non-cryptographic hash functions are also valuable, e.g., in data structures. However, for simplicity, I will sometimes refer to cryptographic hash functions as simply  hash functions . As a note, there are also hash functions with a secret key , known as keyed hash functions. I will not refer to these keyed hash functions here; I will only explain the keyless (or unkeyed ) hash functions.   Cryptographic hash function...
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