31 lines
873 B
Markdown
31 lines
873 B
Markdown
## Lecture 1 (10:00)
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### Caesar Cipher
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#### Dictionary
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- Precalculate encrypted versions of likely words, and when one appears, test the key on the whole message.
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#### Plaintext
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- If you can see certain English commonalities in the cipher, you can make an educated guess. ex. If one letter appears alone, it is most likely an "A" or an "I".
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### DES - Data Encryption Standard
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- Cascaded Transposition.
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- Substitution Ciphers.
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- Initially proposed as 128-bit, US Gov enforced 56-bit. Wonder why????
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- `2^128` - `3.4x10^38` combinations. `5x10^19` years to do half at 100 billion keys per second.
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- `1^56` - `7.2x10^16` combinations. `4` days to do half at 100 billion keys per second.
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### Current State
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- (1999) Triple DES - 112bit -> 128bit standard
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- (2002) AES - 128bit -> 256bit
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# Assessment
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## 4pm 27th Nov Deadline
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- 50% of mark, questions on blackboard
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