Wifi only accepts passwords of 5 or 13 characters

Looks like you are using WEP encryption.

• For a 40 bit WEP network the password is 5-characters.
• For a 128 bit WEP network the password is 13-characters.

Change your encryption to WPA. WPA uses either a passphrase (a shared secret) that is comprised of 8 to 63 characters or a fixed-length of 64 HEX characters.

Oh ... if your network card and/or router does not support WPA (doubt it though since it became available in 2003) you need to buy new hardware.

Regarding the side of the network card. Click the connection icon at the panel, edit connections, choose the wireless and Edit...

Regarding the router you are on your own ;)

A little correction:

WEP 64bit (not 40 as often it is reported): requires 40 bits (from a given password) + 24 (from an initialization vector); 40 bits means 10 hexadecimal digits or (as a restriction) 5 ASCII characters

WEP 128bit: requires 104 bits (from a given password) + 24 bit from the Initialization Vector; hence the given password can have 26 hexadecimal digits (4*26=104) or - as a particular case - 13 ASCII characters

In order to convert a passphrase, having any length, to the sizes enumerated above you need an algorithm which must be matched both in the device (Access Point or Ad Hoc) and in the connecting apparatus (PC or phone)