Try this
Code:
[Setup]: Password
Description:
Specifies a password you want to prompt the user for at the beginning of the installation.
When using a password, you might consider setting Encryption to yes as well, otherwise files will be stored as plain text and it would not be exceedingly difficult for someone to gain access to them through reverse engineering.
The password itself is not stored as clear text; it's stored as a 160-bit SHA-1 hash, salted with a 64-bit random number. (Note: When encryption is enabled, this stored hash is not used for the encryption key; a different hash with a different salt is generated for that.)