Crate strong_box

Secure symmetric encryption using modern algorithms and affordances.

If you want to encrypt something that only someone with the same key can decrypt, and you want the most up-to-date algorithms and security properties (such as Additional Data validation), then StrongBox is for you.

A StrongBox exists to encrypt and decrypt data. It uses a single key to encrypt all data, and can decrypt data that was previously encrypted with any key in the list.

The ability to specify a list of decryption keys allows for periodic key rotation, without losing the ability to decrypt old ciphertexts. This is important because every symmetric cipher scheme is weakened when many plaintexts (in the “billions” range, so it’s usually OK) are encrypted with the same key, so it’s worth rotating your keys now and then. You simply generate a new key, specify that as your encryption key, and make sure the list of decryption keys includes the new key and all the previous keys that any remaining valid ciphertexts may have been encrypted with.

The encryption context is used to provide protection against attacks involving substituting one ciphertext for another. This Security StackExchange answer is an excellent explanation of why an encryption context is useful. If for whatever reason you don’t have an appropriate context, you can use b"" as the context, but remember that the same context must be specified for both encryption and decryption.

Other Kinds of StrongBoxes

If you have multiple different kinds of data to encrypt (say, different fields of a database), it’s safer (on many fronts) to encrypt the different kinds of data with different keys. To facilitate that, you can create a StemStrongBox, and “derive” new StrongBoxes that use keys derived from the keys in the StemStrongBox. This keeps you from having to manage great masses of keys – instead, just have one set of “root” keys, and derive all the other ones you need. Of course, you can derive another StemStrongBox from that one, and so on, creating a whole “tree” of StrongBoxes.

You can also create a RotatingStrongBox, that automatically rotates its keys according to a fixed schedule, and maintains the ability to decrypt ciphertexts encrypted by keys from a bounded number of previous rotations.

Finally, there is the SharedStrongBox, which anyone with a public key can use to encrypt data that only someone with the corresponding private key can decrypt.

Re-exports

pub use ::ciborium;

Structs

Key

A key used by various kinds of StrongBox for encrypting or decrypting data.

RotatingStrongBox

A StrongBox variant that uses a different set of keys for each period of time.

SharedStrongBox

SharedStrongBoxKey

StaticStrongBox

A secure symmetric encryption container, supporting key rotation and AAD contexts.

StemStrongBox

A way to derive many StrongBoxes from one set of keys.

Enums

Error

Traits

StrongBox

Core trait that all the various forms of encrypting StrongBoxes implement to provide encryption / decryption functionality.

Functions

generate_key

Create a key suitable for use in a StrongBox.