README.TXT

File Signature 
 
 
The SIGNFILE sample is a console application that signs files. Files 
signed with this sample can be later verified with the VERIFILE sample. 
 
Note that the INITUSER sample (or equivalent) must be run prior to running 
these samples, in order to create a key container for the default user. 
 
Usage 
----- 
 
The SIGNFILE sample is run from the command line as follows: 
 
    signfile <source file> <signature file> <description> 
 
The <source file> argument specifies the filename of the file to be signed, 
and the <signature file> argument specifies the filename of the file in which 
to place the signature data. The <description> argument specifies a textual 
description of the data being signed. This can consist of empty quotes ("") 
if no description is required. See CryptSignHash in the online documentation 
for more information on signatures and description strings. 
 
The VERIFILE sample is run with the same arguments as SIGNFILE. If the 
contents of the source file, signature file, or description string has 
changed in any way from when the file was originally signed, the program 
will fail. 
 
Exercises for the Reader 
------------------------ 
 
1. These samples would be more useful if the signature public key was stored 
   in the signature file along with the signature data. This public key would 
   need to be wrapped in a certificate (also known as a credential) to protect 
   it from unauthorized modification. If this were to be done, then the data 
   file and its signature could be verified by anyone, even if the original 
   key pair used to produce the signature is destroyed. 
 
2. The SIGNFILE sample could be easily modified such that the description data 
   is stored in the signature file (in a non-encrypted format) along with the 
   signature data. The VERIFILE sample could then read the description from 
   the signature file, instead of requiring it as a command line argument.