YubiKeys are USB tokens that act like keyboards and generate one-time passwords. This package contains a server written in PHP for use with Apache that decrypt YubiKey One-Time Passwords (OTPs), normally only used by YubiKey OTP validation servers. The architecture is that a set of validation servers manage the token counters and respond to OTP requests from clients, and utilize a set of back-end YubiKey Key Storage Module (KSM) servers to perform the actual AES key decryption. The protocols are openly published. This implementation store the AES keys in a database unencrypted, which can be protected using file-system encryption mechanisms Another KSM implementation is available in the yhsm-yubikey-ksm package that use the YubiHSM hardware to protect the decryption process. Sometimes the KSM runs on another server than the validation server, but it is possible to run both on the same machine. After installing and configuring this package you will have a YubiKey KSM server up and running via Apache.