The Code4use WPA Pre-shared Key Generator provides an easy way to convert a WPA passphrase and SSID to the 256-bit pre-shared ("raw") key used for key derivation.
WPA-PSK (pre-shared key) mode, this is designed for home and small office networks and doesn't require an authentication server. Each wireless network device encrypts the network traffic by deriving its 128-bit encryption key from a 256 bit shared key. This key may be entered either as a string of 64 hexadecimal digits, or as a passphrase of 8 to 63 printable ASCII characters. If ASCII characters are used, the 256 bit key is calculated by applying the PBKDF2 key derivation function to the passphrase, using the SSID as the salt and 4096 iterations of HMAC-SHA1. WPA-Personal mode is available with both WPA and WPA2
Pre-shared key WPA remain vulnerable to password cracking attacks if users rely on a weak password or passphrase.
Brute forcing of simple passwords can be attempted using the Aircrack Suite starting from the four-way authentication handshake exchanged during association or periodic re-authentication.
To further protect against intrusion, the network's SSID should not match any entry in the top 1,000 SSIDs as downloadable rainbow tables have been pre-generated for them and a multitude of common passwords.