# Encryption Definition

## What is Encryption?

Encryption transforms data into an unreadable form using a secret key. Once data has been encrypted, the secret key is needed to decrypt and read it. For this reason, encryption is commonly used to protect data confidentiality.

## How Does Encryption Work?

Encryption algorithms are mathematical functions designed to make data unreadable. One of the marks of a good encryption algorithm is that the encrypted data — called a ciphertext — is indistinguishable from randomly generated bits (1’s and 0’s).

Encryption algorithms use a secret key to obfuscate data in a way that is both secure and reversible. Based on how these keys work, encryption algorithms can be broken up into two groups:

**Symmetric:**Symmetric encryption algorithms use the same secret key for encryption and decryption. These algorithms tend to be more efficient than asymmetric algorithms — making them better for protecting large amounts of data — but they require the sender and recipient to have established a shared secret key in advance.**Asymmetric:**Asymmetric or public key encryption algorithms use a public key for encryption and a private key for decryption. Since the public key is public, there is no need to share a secret key in advance of sending encrypted data. Additionally, the design of asymmetric encryption algorithms allows them to be used to generate digital signatures as well, which can be used to prove data integrity as well.

In both cases, the computer encrypting the data will use the original message — called a plaintext — the encryption algorithm, and the key to scramble the data. The data can only be unscrambled with the secret key, making it safe to store on an untrusted computer or transmit over the Internet. In fact, breaches of encrypted data aren’t even considered data breaches unless the key was exposed as well.

When data is encrypted, the algorithm to be used should be publicly known. The most widely used encryption algorithms — such as AES, RSA, and Blowfish — are all public and have undergone extensive review by cryptographers. This makes it much less likely that these algorithms have hidden flaws that could render them vulnerable to attack. When encrypting data, the only secret should be the secret key.

## What are Post-Quantum Encryption Algorithms?

Asymmetric or public key cryptography uses two related keys. The relationship between these keys is a one-way mathematical function where performing some operation is much easier than reversing it.

For example, the complexity of multiplying two prime numbers together grows polynomially with their length, while factoring the result has exponential complexity. This difference in complexity means that it’s possible to find a length for a secret key where multiplication is relatively easy while factoring is nearly impossible.

Quantum computing changes this. With a quantum computer, multiplication and factoring have about the same complexity, making it infeasible to create a secret key that is both usable and secure. Once large enough quantum computers are available, several “classical” asymmetric encryption algorithms will be broken.

Post-quantum encryption algorithms use problems that are still “hard” for quantum computers to solve. These algorithms will replace classical algorithms once quantum computing becomes a real threat.

## Conclusion

Encryption scrambles data in a way that makes it unreadable without access to the right key. This makes it an effective protection for data confidentiality and a fundamental part of the modern Internet. However, the protection that encryption provides is only as strong as the protection on the private key.