You
can obtain this tool from the Microsoft Knowledge Base at
http://support.microsoft.com/kb/
841290/
.
Besides using this utility to track the fingerprints of your files for your own use, you can use it
create a cryptographic hash for other people. When you send someone a file through email, they
have no idea whether someone else has intercepted the message and changed the file. Perhaps this
third party added a virus. The person receiving the file won??™t know who added the virus to the file,
but they??™ll blame you. Supplying a hash value for each file as part of your upload assures the recipient
that they can check and validate the attachment.
Other utilities do provide a form of file integrity. However, the majority of these utilities rely on
a CRC, which is an insecure method of determining file validity because CRC doesn??™t always detect
changes. The FCIV utility relies on the Message Digest 5 (MD5) or Secure Hashing Algorithm 1
(SHA-1) hashing methods. Using either of these two methods is very secure because every file generates
a different result. Consequently, if someone as much as changes the case of a letter inside the
file, you know about it.
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