Questions tagged [symmetric]
Symmetric cryptosystems assume two communicating entities share a pre-established secret key.
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Is it possible to use Diffie-Hellman protocol for symmetric group?
I was asked this question during one of my first cryptography classes, and I'm not sure if I understand it correctly. To begin, I know that after using the Diffie-Hellman protocol (which itself is ...
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Mathematical approach to symmetric cryptography
I'm no mathematician but when thinking about block ciphers such as AES I find it much easier to think of them as a mathematical function $f$ (rather than an 'algorithm') such that $c=f(m,k)$ with $c$ ...
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Can you use ChaCha20 as one-time pad?
My knowledge of cryptography nothing beyond basic so I am by no means an expert, but I do know a bit of undergraduate mathematics including number theory.
I know that stream ciphers like ChaCha20 is ...
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Does Qrypt's BLAST protocol based on "Doubly-Affine Extractors" use public-key or symmetric-key cryptography?
The company Qrypt states that "Key distribution based on asymmetric algorithms is a weak link for cryptography" and claims to "enable encryption without distributing encryption keys&...
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Is DES/2DES/3DES still used?
I checked a related question, but I still did not find the answer I was looking for.
Specifically, do we have any statistics on the usage of DES/2DES/3DES?
It seems from here that credit card systems ...
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Do I need to use unique IVs if all encrypted data is unique?
I am designing a service where each user has both a unique 256-bit private and public ID. These IDs should be derivable from one another, but only within the backend of my service (as to not expose ...
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Is a Shift Cipher with Random Insertions Unbreakable?
Imagine an Encryption Algorithm which applies a classic Shift Cipher (also called Caesar or ROT-X) to a text (with only lowercase [a-z] and the space ...
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Are semantic security and indistinguishability equivalent for symmetric key cryptosystems?
I've seen a lot written about how, in the context of public key cryptosystems, these definitions are equivalent. Is the same true of symmetric key cryptosystems? If so, what are the precise statements ...
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Does this protocol description and design look sound?
I am working on a tool that uses password derived keys for AES and a selectable modes of operation to encrypt (and later decrypt) text for storage on an insecure media. The tool is constrained to ...
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Web app server side encryption scheme
I'm asking if this encryption scheme would increase the security of the user's data. Here's how it would work:
The user would create an account (username + password). An encryption key (symmetric) is ...
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Shared Key message-encryption multiple receiver communication
Say there are 5 parties. 1 is the sender, and 4 are the receivers.
The sender has a unique shared key with each receiver.
k1 - between sender and receiver1
k2 - between sender and receiver2
k3 - ...
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In Symmetric encryption where Alice and Bob message each other, how can both decrypt the same data?
I first posted this question on StackOverflow but they told me it belongs here instead:
https://stackoverflow.com/questions/77856486/in-symmetric-encryption-where-alice-and-bob-message-each-other-how-...
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How does SMB authentication work?
When I learned about the inner workings of the TLS protocol and what exactly it protects a connection against, I was surprised to learn that even asymmetric encryption can be defeated by a MITM attack ...
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Key-dependent cipher generation
Is there any cryptanalysis possible if the cipher itself is deterministically derived from key material?
For example, suppose you have n building blocks (ARX primitives, AES ops, other primitives) and ...
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Security of this MAC scheme
I'm studying for a cryptography exam, I have this question from a past exam:
Consider the MAC with key $k$, based on a block cipher $E_{(k)}$ with block size $n$, and a collision-resistant hash ...
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