**Encryption is used to transform data into a form that can no longer be read by unauthorized persons. Digital keys (key files) are used for encryption in symmetric or asymmetric encryption processes.**

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## What is encryption?

Encryption applies algorithms and procedures to transform data into a form that can no longer be read by unauthorized persons. The data cannot be readably accessed again until it has been decrypted.

Ciphering is a term often used synonymously with encryption. Digital or electronic codes, the keys, are used for encryption and decryption. The keys represent a kind of secret code with which it is possible to transform data from plain text into cipher text and vice versa.

Encryption is used on the Internet to transmit data, such as payment information, e-mails, or personal data, confidentially and protected from manipulation. Data is encrypted using various cryptographic methods based on mathematical operations. The field of research that deals with these procedures is called cryptography.

Depending on the encryption methods used, it is more or less easy to crack cipher texts or keys. If state-of-the-art cryptographic methods with large key lengths are used, they work very securely and are almost impossible to compromise. In principle, a distinction can be made between symmetric and asymmetric encryption techniques. Asymmetric methods have only been known for a few decades. Nevertheless, they represent the most frequently used procedures in digital communication.

## The goals of encryption

Several goals are pursued with the encryption of data. Essentially, these are the following three goals:

- Confidentiality of the data
- Integrity of the data
- Bindingness and authenticity of the source

Encryption is intended to ensure that only authorized recipients can read the contents of the encrypted data. Thus, the data remains confidential at all times. Thanks to the integrity of the data, it is possible for the recipient to determine beyond doubt whether any manipulation or modification of the data has taken place.

Authenticity and bindingness ensure that it is clearly verifiable whether the data actually originates from the specified source. The source is binding because the provenance of the data cannot be disputed.

## Encryption method

The encryption procedure is a mathematical algorithm that encrypts and decrypts the data. The encryption procedure usually also specifies how keys can be exchanged or how authenticity and integrity can be verified. Depending on the procedure, symmetric or asymmetric techniques are used. Hybrid encryption methods combine both symmetric and asymmetric techniques.

## Symmetric encryption methods

Symmetric encryption methods encrypt and decrypt data using a single key. For this, the source and destination of the data must have the same key. If the secret key is passed on or lost, the security of the data is no longer guaranteed. Critical actions for symmetric encryption methods are the distribution, storage, and exchange of the keys.

Modern symmetric methods are based on the block or stream encryption. Whereas in-stream ciphering the data is encrypted one after the other and one by one, block ciphering divides the data into blocks of a certain length before encryption. These are then encrypted according to a defined sequence or interleaving. Known block ciphers are AES, MARS, Twofish, and Serpent.

## Asymmetric encryption methods

Asymmetric encryption methods use two different keys. These are a public key and a private key. The public key can be made available to anyone and is used to encrypt the data. The private key must be kept strictly secret. It is the only key that allows the data encrypted with the public key to be decrypted.

The underlying complex mathematical algorithms of asymmetric methods mean that encryption and decryption require more computing capacity and are generally slower. Combinations of symmetric and asymmetric methods are therefore often used. In this case, they are hybrid procedures. Public-key encryption is an asymmetric encryption method; the best-known implementation is PGP (Pretty Good Privacy).