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How Tink works

Primitives

Tink uses primitives as cryptographic building blocks. A primitive defines the details of a cryptographic algorithm and the key type. An example of a primitive is Authenticated Encryption with Associated Data (AEAD), which exposes an interface for encrypting (Encrypt) and decrypting (Decrypt).

Key types

A key type implements a specific primitive. Most primitives have several key types to choose from, depending on your requirements for security, running time, and space. For example, AES128_GCM is an AEAD; it is fast and effective for most needs.

Keysets

Tink uses keysets for managing keys. A keyset is essentially a set of keys that facilitate key rotation. Noteworthy properties of a keyset are:

  • Each key in a keyset has a unique id, which is unique within a keyset. This id is usually added as a prefix to each produced ciphertext, signature or tag to indicate which key was used (see how Tink tags ciphertexts for more info).
  • Only one key at a time in a keyset is primary. A primary key in a keyset is the key "in use" at the moment.
  • All the keys in a keyset must be implementations of the same primitive (such as AEAD), but can have different key types (for example, an AES-GCM and XCHACHA20-POLY1305 key).

Each Tink implementation provides APIs to create/edit keysets. However, we recommend using Tinkey our CLI tool.

Keyset handles

Users operate over a keyset via keyset handles. A keyset handle limits the exposure of the actual sensitive key material. It also abstracts a keyset allowing users to obtain a primitive that "wraps" the entire keyset. For example, one can get an AEAD primitive of a keyset with N keys; encryption and decryption with the obtained primitive will use the primary key in the keyset.

Next steps

It sounds complicated, but we'll help walk you through. First, set up Tink. Then, use our examples to help choose a primitive and key type.

I want to:

Need advice?

Picking a primitive can be tricky. If the use cases here don't fit your needs, ask a question on StackOverflow.