Symmetric crypto

The exchange of a shared secret between a server and a client can be achieved with public-key cryptography:. After getting the symmetric key from the server, we can use CryptoKit to create a SymmetricKey type for further usage:. The current state of the art in symmetric-key encryption is a cipher called AEAD.

We already looked at signing with public-key cryptography in the previous article. For that, we use the previously shared secret key to sign the digest of the data and then send both, the data and the signed digest to the server. The server uses the same key to validate the data. In the code example above, authenticationCode is our signed digest that we send to the server along with the actual data.

Checking the validity of authenticationCode is similarly simple:. And that's basically it. CryptoKit allows us to apply symmetric cryptography signing, encrypting and decrypting data with a few lines of code. That's pretty awesome! Receive a monthly newsletter about the latest articles and tips. Cryptographic hash functions in CryptoKit for iOS. Use cases of cryptographic hash functions and how to implement them in iOS. Public-key cryptography with CryptoKit for iOS.

Using CryptoKit to increase security in iOS applications. Learn about the life cycle of a SwiftUI application. How to add text input actions to iOS push and local notifications. Learn how to define and handle a notification action that allows custom user text input. How to add and handle actions for iOS push and local notifications.

Block ciphers are typically considered to be more powerful and practical primitives than stream ciphers, but they're also slower. Stream ciphers encrypt each unit of plaintext such as a byte , one unit at a time, with a corresponding unit from a random key stream. The result is a single unit of ciphertext. These algorithms are useful for authentication and for establishing secure communication channels when it is inconvenient to share a symmetric key in advance.

An encryption scheme is called asymmetric if it uses one key — the public key — to encrypt and a different, but mathematically related, key — the private key — to decrypt. It must be computationally infeasible to determine the private key if the only thing one knows is the public key.

Therefore, the public key can be distributed publicly while the private key is kept secret and secure. Together the keys are referred to as a key pair. Another more common name for asymmetric encryption is public-key cryptography. Public-key cryptography is typically based on mathematical problems that are relatively easy to perform but cannot be easily reversed.

These include factoring a large integer back into its component prime numbers and solving the elliptic curve discrete logarithm function. The RSA algorithm is based on the practical difficulty of factoring the product of two large prime numbers. Elliptic-curve cryptography is based on the difficulty of finding the discrete logarithm of a random point on an elliptic curve given a publicly known point. Javascript is disabled or is unavailable in your browser.

Please refer to your browser's Help pages for instructions. Symmetric algorithms Asymmetric algorithms. Cryptographic algorithms. Topics Symmetric algorithms Asymmetric algorithms. Document Conventions. Cryptography concepts.

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