Chapter 3 Cryptography 83
Applications of Cryptography

ASCII Encoding and Decoding

ASCII encoding and decoding is required when you need to send encrypted or signed
data using communication protocols that allow transmission of printable characters
only. In this case, the application must convert the encrypted 8-bit values to a string of
printable characters. Crypto-C uses the Internet RFC1113 method for implementing
ASCII-encoding. The Internet Draft RFC1113 is a publication that describes this
system.
Applications of Cryptography
Crypto-C offers application developers the tools to add privacy and authentication
features to software and hardware systems. This section discusses a number of areas
where such features are useful.
Historically, privacy has been the main use of cryptographic techniques. In these
applications, cryptography is used to hide critical information from attackers or
unauthorized personnel. Crypto-C provides algorithms and methods for encrypting
data in a variety of applications.
Authentication is a cornerstone of the forever-pursued paperless office. Authentication
enables users to prove authenticity and authorship of messages and non-tampering of
data.
Cryptography can be useful in any of the following situations:
•Local applications, to control access and prevent tampering
•Point-to-point applications, to protect the privacy of communications
•Client/server applications, to control access and provide authentication
•Peer-to-peer applications, to protect privacy between nodes

Local Applications

One of the most basic applications of cryptography is local file encryption. There are
many reasons why one would find it useful to encrypt files even if they are not being
transmitted. For example, you can use cryptographic techniques to:
•Save files in encrypted form to protect against unauthorized access.