Week 4 Lecture Reflection1
It is not the only way to break the cipher
The easiest way to calculate and need to find the domain of work
Brute force with heuristics ( 启发)
Entropy ( you can see the lecture 2 )
Degree of randomness ( 程度 )
Complements patterns or order ( 补充性 )
Less patterns = higher entropy
Possible combinations ( 5 letters word 5个字母的单词 )
2^25 possible combinations
Each letter adds 2.5 bits on average
an attack on a security protocol using replay of messages from a different context into the intended (or original and expected) context
fooling the honest participants into thinking they have successfully completed the protocol run
an attack where the attacker secretly relays and possibly alters the communications between two parties who believe they are directly communicating with each other ( active eavesdropping / 主动窃听)
One-way converts any form of data into a unique string of text (fixed size)
Hash functions return the same results each time (deterministic / 确定性)
Hash collisions ( Birthday attack ) — different items map to the same thing
Clustering in data causes clustering in the hash ( 数据中的群集导致哈希中的群集 )
The original message and hash can be tampered with ( 篡改 )
How: computer the hash and check whether is the same
return the same results each time (deterministic)
hard to find two different texts that have the same hash
If the input is changed slightly, the output changes significantly (Avalanche property)
Hard to find two messages with the same hash
If the input is changed slightly, the output changes significantly
Always lie - consider a security question as another password
Use password managers and scrub your social media ( 清除 )
Don’t reuse security questions and answers
people can be easily exploited using persuasion
Increase the time delay between the initial gift and the later request
People believe in the social cues around them
Append a password in the message to be hashed
Message Authentication Code