21 lines
1.1 KiB
Markdown
21 lines
1.1 KiB
Markdown
- #[[CT255 - Next Generation Technologies II]]
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- **Previous Topic:** [[Block Ciphers & Stream Ciphers]]
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- **Next Topic:**
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- **Relevant Slides:** 
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- There are four types of attacks in the context of communication across a network, which are addressed by message authentication:
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- Masquerade (insertion of messages into the network from a fraudulent source).
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- Content modification.
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- Sequence modification.
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- Timing modification (delete or repeat messages).
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- Message authentication is concerned with:
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- Protecting the integrity of a message.
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- Validating the identity of the originator of the message.
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- Validating sequencing & timeliness.
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- Non-repudiation of origin (dispute resolution).
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- # Hash Functions
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- A hash function is a variation of a MAC, which produces a fixed-size hash code ("fingerprint") based on a variably-sized input message.
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- A hash function is public and is not keyed, therefore the hash value must be encrypted.
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- Traditional CRCs are too weak and cannot be used.
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- 128-512 bit hash values are regarded as suitable.
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