What is Themis?

Answer: Themis is an open-source, cross-platform cryptographic library that packages a few high-level, hard-to-misuse primitives instead of exposing raw ciphers. It wraps OpenSSL, LibreSSL, or BoringSSL and ships identical wire formats for iOS, Android, and server languages, so a payload encrypted on one platform decrypts unchanged on another.

Its value is not new cryptography — it is removing the decisions that cause most application-level crypto bugs. You never choose a mode, an IV, a padding scheme, or a KDF; each primitive exposes one encrypt call and one decrypt call, and misuse generally produces an error rather than silently weak output.

Code Example:

# CocoaPods — the default subspec pins an OpenSSL build
pod 'themis'

import themis

// Every primitive follows the same shape: construct, then wrap/unwrap.
let keypair = TSKeyGen(algorithm: .EC)!
let privateKey = keypair.privateKey as Data
let publicKey  = keypair.publicKey  as Data

Key Points:

• Apache 2.0, maintained by Cossack Labs, and independently audited.
• Four primitives only: Secure Cell, Secure Message, Secure Session, Secure Comparator.
• Wire-format compatible across Swift, Kotlin/Java, Go, Python, Node, PHP, Rust, C++.
• Common in fintech and messaging apps that need payload crypto independent of TLS.