Bilateral Key Exchange was an encryption scheme utilized by The Society for Worldwide Interbank Financial Telecommunications

Swift

The swifts are a family, Apodidae, of highly aerial birds. They are superficially similar to swallows, but are actually not closely related to passerine species at all; swifts are in the separate order Apodiformes, which they share with hummingbirds...

 (SWIFT).

The scheme was retired and has now been replaced by the Relationship Management Application (RMA)

Relationship Management Application (RMA)

Relationship Management Application is a service provided by SWIFT to manage the business relationships between financial institutions .RMA operates by managing which message types are permitted to be exchanged between users of a SWIFT service :...

. All key management is now based on the SWIFT PKI that was implemented in SWIFT phase 2.

A Bilateral Key allowed secure communication across the SWIFT Network. The text of a SWIFT Message and the authentication key were used to generate a Message Authentication Code

Message authentication code

In cryptography, a message authentication code is a short piece of information used to authenticate a message.A MAC algorithm, sometimes called a keyed hash function, accepts as input a secret key and an arbitrary-length message to be authenticated, and outputs a MAC...

 or MAC. The MAC ensured the origin of a message and the authenticity of the message contents. This was normally accomplished by the exchange of various SWIFT Messages used specifically for establishing a communicating key pair.

BKE keys were generated either manually inside the SWIFT software, or automatically with the use of an SCR or Secure Card Reader.

Since 1994, the keys used in the card reader and the authentication keys themselves were 1024bit RSA.