Questions tagged [symmetric]
Symmetric cryptosystems assume two communicating entities share a pre-established secret key.
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Is using the same IV in AES similar to not using an IV in the first place?
So if I understand how an IV works with AES, I'm supposed to generate a different IV for every message because using only a key, I will get the same encryption if the message was encrypted twice (...
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Why do we use encrypt-decrypt-encrypt (EDE) in 3DES, rather than encrypting three times?
I'm wondering why we use encrypt-decrypt-encrypt (EDE) sequence in 3DES (also known as DES-EDE, TDES or TDEA) with three keys instead of three times encryption (EEE) with three different keys?
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What is a tweakable block cipher?
Pretty simple question - but I can't seem to find much information about it.
What exactly is a tweakable block cipher?
How do they differ from traditional block ciphers?
What is the 'tweak'? Is it ...
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Why is asymmetric cryptography bad for huge data?
I've been told that asymmetric cryptography requires that the message to be encrypted be smaller than its key length.
Why is this?
I know about hybrid encryption, which uses symmetric encryption to ...
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After ECDH with Curve25519, is it pointless to use anything stronger than AES-128?
Is the following reasoning correct:
After ECDH with Curve25519, the resulting shared secret will be an EC public key with a bit strength of 128 bits.
This public key would then be hashed (let's say ...
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Is AES-128 quantum safe?
I've been reading lately some contradicting messages with regards to the quantum-safe resistance of AES128. First, there are blog posts by Ericsson people like these ones:
Can quantum attackers break ...
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Can I find the encryption key if I know the plain text and the encrypted text (DES and AES)?
If I have the plain text and its output after encryption with a key K1, is it algorithmically feasible to find K1?
I am specifically interested in the cases of DES and AES encryption algorithms.
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Why is public-key encryption so much less efficient than secret-key encryption?
I'm currently reading Cryptography Engineering. After giving a high level explanation of the difference between secret-key encryption and public-key encryption, the book says:
So why do we bother ...
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Is it okay to use an HMAC of the plaintext and a (possibly distinct) key as the IV for symmetric cryptography?
I was thinking of how to create an IV for a block cipher that doesn't require stored state, and I came up with the idea of using an HMAC of the (padded) plaintext and a (possibly distinct) key as the ...
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Why is hybrid encryption more effective than other encryption scheme?
Currently I am learning about Hybrid Encryption but I was not able to find any good study material.
Below is my understanding:
One of the reason why we use ...
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Why not the one-time pad with pseudo-number generator
I am very new to cryptography (so be kind), but I have a question that may seem silly.
If the one-time pad is the perfect cipher and impossible to crack, why would the following algorithm not be one ...
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Deriving Keys for Symmetric Encryption and Authentication
So here's the concept. Rather than storing 2 keys and using a random IV, which presents its own problems (key rotation, ensuring no key is used in more than 2^32 cycles, sharing the keys, etc), is it ...
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How can we reason about the cryptographic capabilities of code-breaking agencies like the NSA or GCHQ?
I have read in Applied Cryptography that the NSA is the largest hardware buyer and the largest mathematician employer in the world.
How can we reason about the symmetric ciphers cryptanalysis ...
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Why does the recommended key size between symmetric and asymmetric encryption differ greatly?
In various articles it is mentioned that for secure communications, the recommended key sizes are 128-bit key size for symmetric encryption (which makes it $2^{128}$ possible keys?) and 2048-bit key ...
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Why do we need asymmetric algorithms for key exchange?
In SSL protocols, both symmetric and asymmetric algorithms are used. Why is it so? The symmetric algorithms are more secure and easier to implement. Why are asymmetric algorithms usually preferred in ...
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