Observability of the Java Virtual Machine

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The JVM is one of the most observable runtimes. It provides us lots of tools for troubleshooting a JVM application in production. 1. Thread observability Threads are how the JVM actually does work. When something is wrong in production, the symptom is almost always a thread: stopped, blocked, leaking etc. Thread dumps work on any JVM with no  instrumentation, no agents, no restarts. <Example project link with /threaddump endpoint>         // (1) Deadlock — two threads grab the same pair of locks in opposite order.         new Thread(() -> grab(LOCK_A, LOCK_B), "deadlock-A-then-B").start();         new Thread(() -> grab(LOCK_B, LOCK_A), "deadlock-B-then-A").start(); http://localhost:8080/actuator/threaddump To list the JVMS, we can use the command below. PS C:\observe-jvm> jps -lv 25296 jdk.jcmd/sun.tools.jps.Jps -Dapplication.home=C:\Program Files\Microsoft\jdk-21.0.3.9-hotspot -Xms8m -Djdk.module.main=...
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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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