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Luhn Algorithm

  The Luhn Algorithm, also known as the modulus 10 or mod 10 algorithm, is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers. It helps to detect accidental errors in the input data. Here's a step-by-step explanation of the Luhn Algorithm: Consider the example of an account number “ 79927398713 “.  Starting from the rightmost digit and moving left, double the value of every second digit. If the doubling results in a number greater than 9, then add the two digits.         Second digits from right most are 1, 8, 3, 2, 9 Doubling those digits give 2, 16, 6, 4, 18        Adding double digits give 2, 7, 6, 4, 9 Sum all the digits, including both the untouched digits and the doubled digits. Hence sum is 7 + 9 + 9 + 4 + 7 + 6 + 9 + 7 + 7 + 2 + 3 = 70 If the total modulo 10 is equal to 0, then the number is valid according to the Luhn Algorithm.       ...
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JWT (JSON Web Token)

 JWT (JSON Web Token) is a compact, URL-safe means of representing claims to be transferred between two parties. The claims in a JWT are encoded as a JSON object and are typically used to authenticate and authorize users in web applications. Here's an overview of JWT and its components: Structure of a JWT A JWT consists of three parts: Header Payload Signature These parts are separated by dots ( . ), forming a string that looks like this: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c 1. Header The header typically consists of two parts: the type of token (which is JWT) and the signing algorithm being used, such as HMAC SHA256 or RSA. Example: json { "alg" : "HS256" , "typ" : "JWT" } This JSON is Base64Url encoded to form the first part of the JWT. 2. Payload The payload contains the claims, which are statements about an entit...
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Security in General

 The key concepts related to security in computing: hashing, symmetric encryption, asymmetric encryption, digital signatures, SSL/TLS protocol flow, and OAuth 2.0 flow. 1. Hashing Purpose : Hashing is a one-way function used to convert data into a fixed-size hash value, which is typically used for data integrity verification. Characteristics : Deterministic: The same input always produces the same output. Irreversible: It should be computationally infeasible to reverse the hash to retrieve the original data. Collision-resistant: Two different inputs should not produce the same hash output (though some algorithms like MD5 and SHA-1 are now considered weak). Common Algorithms : MD5, SHA-1, SHA-256, SHA-3. 2. Symmetric Encryption Purpose : Symmetric encryption uses the same key for both encryption and decryption, making it efficient but requiring secure key distribution. Use Cases : Encrypting data at rest, encrypting data in transit (e.g., SSL/TLS), and securing communication channel...
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