Public key cryptography describes all cryptographic algorithms which have a pair of keys, one key that performs encryption and one key that performs decryption. One of these keys is made available publicly, allowing anyone to send messages that only the holder of the private key can read. You should ...
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What happen if a asymmetric crypto-system deals with only one key
Assume there is a crypto algorithm that deals with matrices to encrypt and decrypt. Regardless of the specification of such algorithm, what if the algorithm assumes that two parties can securely agree ...
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Requiring a “supervisor” key pair and a “user” key pair to decrypt multiple-recipient messages
I've been toying with some encryption scenarios recently. One of the hard ones I came across is a multi-party system.
So we have
Bob -- The person who sends the message (and knows it's recipients)
...
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Why is proof-by-reduction needed (for Elgamal proof of security, for example)?
The textbook proof for Elgamal encryption basically reduces to the Decisional Diffie-Hellman assumption (DDH).
Elgamal:
$Gen(.): x \xleftarrow{R} \mathbb{Z}_p$; $Enc(m,g^x): r \xleftarrow{R} ...
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Ring Signature - paper/code difference in trying to solve inverse trap door function?
there is a paper on ring signatures and a python implementation of it here.
The Step 4 in the paper describes $y_s = v =C_k,_v(y_1, y_2, ... y_r)$ for all $1 \leq i \leq r$ where $i \neq s$. The ...
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RSA reencryption scheme
Is there such an algorithm that would allow to upgrade the encryption of a RSA-encrypted message without revealing the plaintext to the untrusted user?
Basically, such an algorithm would probably be ...
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Prevent/minimize replay attacks in public message board
Assume we have a public message board where anyone can send a message to. If plain messages are used, anyone can impersonate anyone. The goal is to disallow impersonations. We can use public key ...
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83 views
Determining the algorithm used to generate a digital signature
I have a string "abcd pqrs". This string is digitally signed with an X.509 certificate (with its private key) and it produces a signature.
From the signed string, is it possible to find out what ...
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In S/MIME, are the same certificates always used to sign and encrypt messages?
My assumption is that S/MIME almost always utilizes certificates as follows:
My certificate can be used to allow people to encrypt messages and send them to me.
My certificate (the same ...
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Cryptographic Protocol using NaCL
Why?
I wanted to add some security and privacy to a chat-type server for playing various games (with a few things that are done on the server to limit cheating). Going by the "Don't implement ...
