A message is to be transferred from one principal (sender) to another (recipient) across some internet service. The two must cooperate for the exchange to happen. A logical information channel is established by defining a route through the internet from the source to the destination by the principals’ cooperative user of communication protocols (e.g. TCP/IP).
All the techniques for providing security have two components:
- A security-related transformation on information to be sent:
- encryption of the message to make it unreadable by opponent, and/or
- addition of a code that can be used to verify identity of sender
- Some secret information shared by the two principals (which is hoped to be) unknown to the opponent: such as an encryption key.
Trusted Third Party (security)
A trusted third party may be needed to achieve secure transmission:
- they are responsible for distributing secret information to the two principals while keeping it from any opponent
- needed to arbitrate disputes between the two principals concerning authenticity of a message transmission
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This model shows 4 basic tasks:
- design an algorithm for performing security-based transformation
- generate secret information to be used w/ algorithm
- develop methods for distribution of secrets
- specify a protocol to be used by the two principals that uses the security algorithm