A modular encryption device includes a chassis configured to mount in a rack with a networking device and sets of ports mounted on the chassis. Encryption cards are mounted in the chassis of the modular encryption device between ports of the sets of ports such that network traffic flowing through a set of ports flows through one of the encryption cards. The encryption cards of the modular encryption device are configured to encrypt and decrypt network traffic flowing between the networking device and a remote device. In some embodiments, a modular encryption device may encrypt and decrypt network traffic flowing between multiple networking devices and multiple remote devices. Also, in some embodiments, components of a modular encryption device are removable and replaceable such that the modular encryption device can be reconfigured by exchanging the components.