In this post we provide the definition of finite groups and we show a few examples meaningful for cryptography and blockchain Def. Finite Groups Def. A group is a set together with an operation combining two elements of , which satisfies the following properties: Closeness: The group operation is closed: Read more…
This post is a collection of basic topics needed for a proper understanding of Cryptography. Cryptographic Systems Primal goal: allow two people to exchange confidential information even if they can only communicate via a channel monitored by an adversary Symmetric Cryptosystem A 5-tuple Where are sets of possible keys, messages, Read more…
Spring Data JPA simplifies database interactions in Java applications, by managing the complexity of object-relational mapping (ORM). At the hearth of this feature are annotation mapping Java objects to DB tables. In this reference, I explain how to use annotations such as @Entity, @Table, @Column, @Id, @ManyToOne, and more, using Read more…
A Binary Search Tree (BST) is a Binary Tree data structure with nodes ordered according to the following property: For each node with a key K, all the left children have values lesser than K, and the right children greater than K. BSTs allow fast lookup, addition, and removal of Read more…
Binary search is an algorithm to find the position of a target value within a sorted array by recursively halving the number of candidates. Assuming we have a sorted array with n elements, we can binary search a target element in logarithmic time, O(log(n)). Binary Search Algorithm To perform a Read more…
Example of using Docker compose to run nginx reverse proxy with SSL to expose different WordPress web apps on multiple domains. This content can be easily generalized to serve multiple websites with other kinds of web applications. Prerequisites Before starting, you need to check you satisfy the following prerequisites: You Read more…
Java type erasure You can work with java generics, but still, don’t understand type erasure? Let’s look at this example: The generic T is to perform type check at compile-time. To implement this generic, the compiler will: replace the T parameter with the bound classes or Object insert type casts to Read more…
Here is a set of Linux commands used when operating as remote server admin: i.e. find and modify multiple files, sync local and remote files, generate keys, etc. SSH and keygen The first operation for working on a remote server is connecting via ssh. Typically, you connect to the server Read more…
In my local development environment, I have a running database that I want to backup. Find container First, list containers with docker ps, identify the database you want to backup and note down the CONTAINER ID. In my case, the container id is 3f7b373c036d. Backup Create a file named backup.properties Read more…
This article shows how to perform a secure Linux server setup by creating a VPS, adding a sudo user, enabling public key access, activating the firewall, and disabling root access. Linux server Here we consider a few different VPS (Virtual Private Server) providers. Then, we choose a provider and see Read more…