Schlüsselkryptografie

Schlüsselkryptografie, also known as cryptography, is the practice and study of techniques for secure communication in the presence of third parties called adversaries. It involves the use of algorithms and keys to transform readable information, known as plaintext, into an unreadable form, called ciphertext. This process is called encryption. The reverse process, transforming ciphertext back into plaintext, is called decryption.

The security of cryptographic systems relies on the secrecy of the key, a piece of information used by the encryption and decryption algorithms. There are two main categories of cryptographic systems: symmetric-key cryptography and asymmetric-key cryptography.

In symmetric-key cryptography, the same key is used for both encryption and decryption. This means the sender and receiver must securely share the key beforehand. Examples include the Data Encryption Standard (DES) and the Advanced Encryption Standard (AES). Symmetric-key systems are generally faster than asymmetric-key systems.

In asymmetric-key cryptography, also known as public-key cryptography, two distinct keys are used: a public key and a private key. The public key can be shared freely and is used for encryption. The private key is kept secret by its owner and is used for decryption. This system allows for secure communication without the need for prior secure key exchange. The most widely known algorithm is RSA. Asymmetric-key cryptography is crucial for applications like secure web browsing (SSL/TLS) and digital signatures.

Cryptography plays a vital role in modern digital security, protecting sensitive data, ensuring the authenticity of communications, and enabling secure online transactions.