Just Cryptography

Learn Cryptography and Information Security

  • What are Asymmetric algorithms?

    Asymmetric algorithms are very important in cryptography and especially in digital signatures. The first asymmetric cryptography algorithms were introduced by Whitfield Diffie and Martin Hellman in the 1970s. The main difference between classical and symmetric cryptography is that instead of using a key to encrypt and decrypt, you should now use a pair of keys.…

  • What is a Public Key Certificate?

    A Public Key Certificate is a document. We can use it to share a public key directly with other users/people/services. It is also known as a digital certificate or identity certificate. Basically, a certificate tells someone else, that you own a certain public key. That public key can then be used to start a secure…

  • What is a Digital Signature and how does it work?

    A digital signature is a mechanism we can use to verify the authenticity of a message/document. It is usually needed in situations when there is no trust between sender and receiver. We can use a digital signature to verify the author of the signature, to authenticate the content of the message. Also, third parties must…

  • What is a Cryptographic Hash Function?

    A cryptographic hash function is an algorithm that has two main properties: it is a one-way function and is collision-free. As per function definition, it transforms one input into only one output. By one way function we mean that is computationally infeasible to find the input related to a given output. The best attack known…

  • What is a Key Distribution Center (KDC)?

    A Key Distribution Center is the way to automatically distribute keys to support arbitrary connections between pairs of users. The users can be a computer, a process or applications. Each user shares a unique key with the KDC, known as the master key. To understand the use of a KDC we need to understand what…

  • What is an Intrusion Detection System (IDS) and how does it work?

    An Intrusion Detection System (IDS) is a security system that monitors computer systems and network traffic. It searches for malicious traffic that can represent attacks to the system or network. Also, it searches for systems or network misuse. The main goal of an IDS is to detect intrusions and/or react in real-time avoiding the intruder…

  • How to implement the Playfair cipher in python?

    The Playfair cipher is a multiple letter encryption cipher that uses a substitution technique. The steps to implement it are as follows: Create a 5×5 matrix using the secrete key. In this matrix, I and J are in the same cell. you start filling the matrix with the key, then you use the alphabet. Letters…

  • Python implementation of the Caesar cipher

    The Caesar cipher is an encryption technique used by Julius Caesar to send communications that had military importance for his empire. Today is a technique that is studied in Cryptography under the classification of substitution ciphers, a topic that at the same time is under classic cryptography. It is also known as a shift cipher,…

  • Digital certificates validation methods: a comparison

    Digital Certificates validation is an important topic in keeping information secure. In this article, I’ll show you a comparison of these methods. Using public-key cryptography solves the key exchange problem that exists in symmetric cryptography. However, another problem shows up: trust. Does the public key that comes from the other end of the connection belong…

  • OpenPGP: Encryption and digital signature using GpgFrontend

    This article explains what is OpenPGP and how to use it to encrypt and sign documents. You will understand how this standard works and the foundations of the security of hybrid cryptography systems. What is PGP, OpenPGP and GPG? Pretty Good Privacy (PGP) is an encryption system that combines symmetric and asymmetric algorithms for encryption…

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