Key generation facts for kids

Key generation is about creating special secret codes called keys. These keys are super important for cryptography, which is like a secret language used to protect information. When you send a secret message, a key helps to scramble it (encrypt) so only the right person can read it. It also helps to unscramble it (decrypt) when it arrives.

Imagine you have a secret diary. The key to that diary lock is like a cryptographic key. Only with the right key can you lock and unlock your secrets!

There are two main types of secret code systems used today:

• Symmetric-key algorithms: Think of this like a single key that both you and your friend use for a secret box. You both have the same key. If you want to send a secret message, you use this key to lock it, and your friend uses the exact same key to unlock it. Examples include DES and AES. The most important thing is to keep this shared key a secret!
• Public-key algorithms: This is a bit different. Imagine you have two keys: one you share with everyone (your public key) and one you keep totally secret (your private key). If someone wants to send you a secret message, they use your public key to lock it. But only your private key can unlock it! This is very clever because you can share your public key with anyone without worrying about your secrets. RSA is a common example.

Because public-key systems can be a bit slower, many modern systems, like when you browse secure websites (TLS or SSH), use a smart combination of both:

• First, they use the public key system to securely share a small, temporary symmetric key.
• Then, they switch to the faster symmetric key system for the rest of the conversation. This makes sure your online activities are both secure and fast!

Keeping Secrets Safe

The simplest way for someone to try and read an encrypted message without the key is called a brute force attack. This is like trying every single possible key until one works. It's like trying every number combination on a lock until it opens.

To stop this, it's super important to use a long enough key length. Longer keys mean there are many, many more possible combinations. This makes a brute force attack take an incredibly long time, so long that it becomes impossible to do in real life.

Currently, common key lengths are:

• 128-bits for symmetric key systems.
• 1024-bits for public-key systems. The more bits, the harder it is to guess!

How Keys Are Made

In computers, cryptographic keys are usually just very large numbers. How are these numbers created?

Random Key Creation

Sometimes, keys are made using a random number generator (RNG). This is like a special program that creates numbers that seem completely random. There are also pseudorandom number generators (PRNGs). These are computer programs that produce numbers that look random, but they are actually made using a set of rules.

Some PRNGs use something called system entropy. This is like collecting tiny bits of unpredictable information from your computer, like how long it takes you to move your mouse or press a key. This "randomness" helps to create a starting point, or seed, for the PRNG. Using these seeds makes the keys even harder for an attacker to guess.

Keys from Passphrases

In other cases, a key can be created from a passphrase you choose. A passphrase is like a secret sentence or a long password. A special key generation algorithm then uses a cryptographic hash function (like SHA-1) to turn your passphrase into a unique key. This means you don't have to remember a super long, random key, just a memorable passphrase!