What is asymmetric cryptography?

What is asymmetric cryptography?

Asymmetric cryptography, also known as public key cryptography, is a key component of modern digital security. Its approach to encryption allows for secure communication and information exchange even over untrusted channels. Asymmetric cryptography uses two related keys: a public key and a private key.

The public key, as the name suggests, is open to everyone and is used for encrypting messages.

The private key is secret and is used to decrypt encrypted messages.

It is important that a message encrypted with a public key cannot be decrypted except by using the corresponding private key, making the method very secure.

Principle of operation

The process of asymmetric cryptography can be divided into three stages: key pair generation, encryption, and decryption.

• Key Pair Generation: The algorithm creates two mathematically related keys, a public and a private key. The public key is shared freely, while the private key is kept secret.
• Message encryption: The sender uses the recipient's public key to encrypt the message. The encrypted message (ciphertext) is then sent to the recipient.
• Receiving an encrypted message: The recipient uses their own private key to decrypt the encrypted message.

Use cases

Asymmetric cryptography is a versatile tool with a wide range of applications, including:

• Encrypted communication: Enables secure information exchange between two parties on an open network. The recipient can share their public key, which allows anyone to encrypt a message, but only the recipient with the private key can decrypt it.
• Digital Signatures: Ensures the integrity of the message and the identity of the sender. The sender can create a digital signature with their private key, and anyone can verify it using the sender's public key.
• Key exchange: Creating a secure shared encryption key between communicating parties without the need to transmit the key insecurely. For example, Diffie-Hellman key exchange allows for the creation of an encryption key that can be used in symmetric encryption.
• Authentication: Verifying the identity of a user or device using digital certificates that are signed by a trusted entity (certification authority). This is crucial in the use of online banking and other security-critical services.

Common algorithms

Here is a summary of the key algorithms of asymmetric cryptography and their purposes:

RSA (Rivest-Shamir-Adleman)

RSA is one of the oldest and most widely used public key algorithms. It is based on the difficulty of factoring large integers into prime numbers. RSA is used for both data encryption and digital signatures. Its security is based on the difficulty of factoring large numbers, and its security level depends on the length of the keys, typically using at least 2048-bit keys. RSA is an established standard and is widely used in network security, for example in the SSL/TLS protocol during web browsing.

ECC (Elliptic Curve Cryptography)

ECC is a more modern form of public key cryptography based on the theory of elliptic curves over finite fields. It provides the same level of security as RSA with smaller key sizes, making it more efficient and faster. ECC is used in many security protocols, such as SSL/TLS, and in the security of modern mobile devices and IoT devices. An advantage of ECC is that it requires less computational power, which is especially important in mobile devices and IoT environments.

Diffie-Hellman key exchange

Although Diffie-Hellman itself is not a encryption algorithm, it is an important method in public key cryptography that allows for secure exchange of secret keys between parties over an open channel. This method is the foundation for many protocols that create encrypted connections, such as TLS. Diffie-Hellman is vulnerable to "man in the middle" attacks unless it is used in conjunction with a method that verifies the parties' identities, such as digital signatures.

DSA (Digital Signature Algorithm)

The DSA is a standard for creating and verifying digital signatures. It was developed by the United States government and is part of the Digital Signature Standard (DSS). DSA allows for signing documents or messages in a way that the authenticity of the signature can be verified. Its security is based on the difficulty of the discrete logarithm problem. DSA is widely used for creating digital signatures, which is essential for example in electronic commerce and ensuring the authenticity of documents.