12 questions linked to/from Related-key attacks on AES
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### What is a related key?

We talk of related keys and related key attacks, but what is a 'related key'? So in three related parts:- How can one key be related to another key? Is there a metric describing the degree of ...
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### What is the importance of Rcon in Rjindael's key expansion from a security prespective?

I do not see why the Rcon function is important, it looks like a waste of cycles. $$\operatorname{Rcon}(i) = 2^{i-1} \bmod p(x)$$ is in $\operatorname{GF}(2^8)$, ...
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### Do test vectors ensure a cipher is free of backdoors?

If a cipher implementation passes unit tests using test vectors from some trusted source (these for AES, for example), then can we say that it is fully conforming to the specification, and must have ...
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### Can a 1 byte difference in AES 128 bit keys make huge difference in output?

If we take some randomly generated key of AES-128 and we change any random 1 byte of that 16 byte key, will this make huge difference in the AES cipher text generated over same input string? Does ...
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### Choice between AES-128 and AES-256 for password protection in MS Office

Why are we still using the default of AES-128 when password protecting a Microsoft Word document. My answer is and always has been - because its good enough and MS don't recommend changing to AES-256. ...
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### Security of AES in CTR mode with fixed nonce (but different key)

If I am using AES in CTR mode and use a unique key every time but the same nonce, is this secure? If so, does it make a difference if the nonce is public?
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### Post Quantum Symmetric Cryptography

So I am looking for the most secure method of symmetric key cryptography for long term messaging use between two users. I have heard that most symmetric key algorithms are not absolutely compromised ...
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### How do Hash functions work under the hood? [closed]

Using and benefiting from hash functions on a daily basis, I keep wondering how hash functions actually work down in their core. Most of the available resources I found, only explained hash functions ...
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### How often do I need to rotate AES 256 keys

I'm trying to design a protocol for a resource constrained environment. The device has to communicate with a server through an insecure node. My plan is to use AES 256 end to end for all ...
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### Consider the use of double encryption applied to the AES algorithm with two 128-bit keys

Actual Question below. Consider the use of double encryption applied to the AES algorithm with two 128-bit keys. How much storage and computation would be required to execute a meet-in-the-middle ...