Kotlin Language Features Related to Null Handling

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Any software engineer with a Java background would find the null handling features in the Kotlin language interesting. Let's summarize this topic with some examples. Nullable types: In Kotlin, types are non-nullable by default. If you want a variable to be able to hold a null value, you need to explicitly declare its type as nullable using the Type? syntax. For example, String? denotes a nullable string, while String represents a non-nullable string. Safe calls (?.): Kotlin introduces the safe call operator (?.) for handling nullable types. It allows you to safely invoke a method or access a property on a nullable object. If the object is null, the expression returns null instead of throwing a NullPointerException. Example: data class Person(val name: String, val age: Int, val address: String?) fun main() {     // Create a person with a nullable address     val person1 = Person("John Doe", 25, "123 Main Street")     val person2 = Person("Jane Doe", 30,
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A Nice Explanation of the Public Key Cryptography

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Recently I've read the explanation below, which is quite good and easy to understand:

Public key cryptography, also known as asymmetric cryptography, is a cryptographic technique that uses a pair of keys, a public key and a private key, for secure communication and encryption. This system is widely used in various applications, including secure communication over the internet, digital signatures, and secure data storage. Let's dive into how public key cryptography works step by step:

1. Key Pair Generation:

A user or entity generates a key pair consisting of a public key and a private key. These keys are mathematically related, but it is computationally infeasible to derive the private key from the public key.

2. Public Key Distribution:

The user or entity freely distributes their public key to anyone who needs to communicate with them securely. The public key can be shared openly and is used for encryption.

3. Private Key Protection:

The private key is kept secret and securely stored by the user or entity. It should never be shared or exposed to others.

4. Encryption (Sender's Perspective):

   - Suppose User A wants to send an encrypted message to User B.

   - User B's public key is used to encrypt the message. This process is known as encryption.

   - The encrypted message can only be decrypted using User B's private key, which only User B possesses.

5. Decryption (Receiver's Perspective):

   - User B receives the encrypted message and uses their private key to decrypt it.

   - Since only User B has access to their private key, they are the only one who can decrypt and read the original message.

6. Digital Signatures (Sender's Perspective):

   - To digitally sign a message, User A uses their private key to generate a unique signature for the message.

   - The signature is attached to the message and sent to User B.

7.  Signature Verification (Receiver's Perspective):

   - User B receives the message and the attached signature.

   - User B uses User A's public key (which is publicly available) to verify the signature.

   - If the signature is valid, User B can be confident that the message was indeed sent by User A and that it hasn't been tampered with during transmission.

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