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Questions tagged [keys]

Private and secret keys consists of secret information used as input to various kinds of cryptographic algorithms such as encryption, signature and MAC to select the concrete transformation done by the algorithm.

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Multi key layered encryption verification

Is it possible to take some value text like “Hello World!” And encrypt it with a random key. Then take the encrypted message and encrypt it again with another random key. And so on… Then can you write ...
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What is a ciphering key?

In Hebrew language there is the term tzophen (צופן) which means cipher. There is also a term "maphtech hatzpana" (מפתח הצפנה) which means "ciphering key". What is a ciphering key? ...
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Key distribution protocol involves only 2 parties, given E[k1,E(k2,m)]=E[k2, E(k1, m)]

Given an one-key cipher such that: E[k1,E(k2,m)]=E[k2, E(k1, m)] Is there any key distribution protocol that involves only two parties (Alice and Bob) without the key distribution center? The protocol ...
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How to Remove Encryption Key from Python Code

I am trying to remove the encryption (AES) from the improved LSB which is in Python: I want to do comparison on LSB with AES and LSB without AES. The AES is connected to LSB.py, PLShandler.py, main.py....
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Proving you're from the year 2069

Just a question I thought of while playing an amazing game about time travel (13 sentinals aegis rim). What are the most bullet-proof cryptographic methods for proving you've come from beyond a ...
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predict random keys using python [closed]

How can I write a program in python to predict the random key (urandom) that is used for encryption? I tried to search and I couldn’t find anything related to guessing and predicting urandom in python
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Generating multiple keys to decrypt one encrypted file

I've come across this particular design where I have one file encrypted. Then multiple people may want to access the file and I want to generate an individual key for each person, but each individual ...
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Can I decrypt AES-CBC ciphertext if I have the key without IV? [duplicate]

Can I decrypt ciphertext from AES-CBC encryption, if I have the key and ciphertext only?
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How proxy re-encryption works - layman perspective

Here is the use case: A uses B's public key to encrypt a message and sent it to B. In later stages, a new member C joins and B would like to let C be able to see this encrypted message (i.e., give the ...
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Entering a word in a S-Box (like Feistel ciphers do) and keeping the S-Box secret: Could this be called encryption?

Let's suppose I take a data block of 64-bits and use it as an entry in a (big) S-box, and keep the S-box secret. S-box would be the "key". For "decryption" I just enter the result ...
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Generate a key with a size bigger than the hash output length/security, is it possible?

Let's suppose I want to generate a 2048-bit key from a hash function with security up to 512-bits (such as Blake2b). I take 4 high-resolution photos, hash them with a hash output length of 512-bits ...
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Tools/libraries to protect private keys using shamir secret sharing / multi-party computation?

here is the scenario. I want to use the concept of shamir secret sharing (or other multi-party computation methods) to store my private key in the public-key encryption. For example, I use RSA to ...
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How to share decryption ability to others whose public keys are not used during encryption?

as the title says, for example, A uses B's public key to encrypt a message and sent it to B. In later stages, a new member C joins and B would like to let C be able to see this encrypted message (i.e.,...
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Using the hash of the plaintext as the key

I want to start off by being very clear: I'm not designing a system around this, this is 100% a hypothetical I was toying with. Is there any harm in using the cryptographic hash of a plaintext as the ...
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Can the security margin of any Feistel block cipher be multiplied if I just multipy the number of rounds and use different random subkeys each round?

Kaweichel is a port of Blowfish for 64-bit architectures, its key size accepted is 1920-bytes, instead of 16 rounds it has 32 rounds, the double of Blowfish. ICE is a feistel block cipher that has a ...
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Does the security margin of Kalyna block cipher double per for additional 4 rounds? Would be possible to create a version of it with larger key sizes?

I believe this question should be directed to the authors of Kalyna block cipher, but I think they cannot answer me because of the war they are facing in their country actually. I know that AES uses ...
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What would be the disadvantages of very large block sizes in block ciphers?

Let's suppose someone creates a block cipher with 8192-bytes of the block size (65536-bits) or maybe 16384-bytes of the block size (131072-bits). What would be its disadvantages over a block cipher ...
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Let negl1 and negl2 be negligible functions [closed]

can we still consider the second function negligible ? is there any main differences between them?
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How web browsers and WebCrypto API protects secrets

I tried to search and take a look at a way to securely generate or import secret keys on client-side. First I tried to see if it is possible to take advantage of TPM in Windows but as far as I ...
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Protection (nonce addition?) against key discovery in AES 256

I've got a situation where I need to send message ciphered with AES-256. However the content, and therefore length, of the message may be intercepted before (don't ask;)) and the question I was asked ...
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How does biometric authentication add protection to encryption schemes?

I'm wondering since at least 2 offline password management services,Passkeep and Keepass both use biometric authentication in addition to the master password. You need to possess the physical device ...
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Session Key Exchange Algorithm - Finding the Security Flaw

The protocol shown in the Figure is open for an attack that will let an attacker learn the secret value from the server without having to know the key Kcs. Can anyone help in finding such an attack? ...
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Why do most authenticated encryption primitives expect an unpredictable and uniformly random key in order to be secure?

I've noticed that keys for authenticated encryption primitives like AES must be unpredictable and uniformly random in order to be secure. IV values and seeds for PRNGs also have to be unpredictable ...
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How are keys shared safely for block / stream encryption?

I've picked up a grad level computer security class. I read a brief overview on block and stream encryption. I understand and have used PGP in the past and it make since to share your public key. ...
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storing private key on the client-side (with and without Web Cryptography API)

I'm trying to understand what are my options(and best practices) regarding storing private key on the client-side. There's a Web Cryptography API that can generate pair of keys with non-extractable ...
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Multiple Encryption Using GCM For Multi-Key Security

Multiple Encryption For Multi-Key Security I have a hypothetical question about multiple encryption after reading Matthew Green’s blog on multiple encryption. For those who are familiar with GCM…I ...
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Is there a Stream Cipher, with the ability of key reusing and what would be the advantages and applications of this kind of stream cipher?

In the case of a OTP (One Time Pad), if we encrypt two different images with the same key, then two encrypted images will be generated. Then if these two encrypted images are mixed with bitwise xor ⊕, ...
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Usage of cookies in IKE

While creating secret keys in IKE protocol, sides use cookies but I did not understand where they come from, how they are generated and why they are used. Can someone explain? Thanks.
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What is the difference between key exchange protocol and key distribution protocol? [duplicate]

Can someone please explain what exactly is the difference between key exchange protocol and key distribution protocol? I looked on the Internet but it was not clear to me. I would be grateful if ...
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CTR HMAC SHA1 vs GCM Key management

The protocol SRTP uses by default AES in CTR mode with HMAC-SHA1. For my thesis I want to research if GCM would be a better option. Therefore I read following discussion. There the answer was that GCM ...
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What percentage of the keyspace should be brute-forced to find an equivalent key if the block cipher has?

I have been reading the Hasty Pudding Cipher specification and the author make clear that the cipher has some equivalent keys if the keyspace is larger than 8192-bits: ...
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Generating a public-private key pair from another key pair

Is the following problem a known cryptographic problem? Find algorithms for functions $f$ and $g$, such that $$ f(x, \alpha_{enc}) \rightarrow \beta_{enc}\\ g(x, \alpha_{dec}) \rightarrow \beta_{dec} $...
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Argon2 allows a huge key length in input, but does it really provide the security of the key provided?

I read the Argon2 specification. It says in 3.1 (Page #5): Secret value K (serves as key if necessary, but we do not assume any key use by default) may have any length from $0$ to $2^{32}\text{-}1$ ...
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Trimming uniformly random input for elliptic curve private keys

Imagine there is 256-bit uniform input from CSPRNG. Suppose there is a curve like secp256r1 whose curve order is slightly less than 256 bits. We cannot just ...
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Asymmetric key Cryptography

In asymmetric key cryptography, public key is available to everyone. If an attacker encrypts the message sent by another user then the receiver might receive that message. Then how the security is ...
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Is this a well defined sharing scheme to propose

A proposed secret sharing scheme: Suppose that $p:S\times Y\to X$, with $|Y|\geq|S|$ is a cipher where, $y\in Y$ is the key and $x\in X$ the code, $p$ is bijective, namely $(x,y)$ is associated with ...
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Which solution is the more protected?

I am wondering which of these two solutions is better for security on the long run. The problem is: Alice and Bob exchange a secret key/private key. Then they go far away from each other and never ...
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Deterministic key selection using iterative value comparison - how dumb was this?

Just to start, this is mainly a curiosity question that's been nagging me for a while. I did a fair bit of googling to see if someone has already performed a righteous expose of this silly idea, but ...
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How much information is required to specify a new variant of AES beyond the key length and the number of rounds?

Three different versions of the Advanced Encryption Standard (AES) have been standardized, which use keys of bit length 128, 192, and 256 respectively. They also use different numbers of rounds: 10, ...
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Can the security of Salsa20/Chacha20 be expanded to 448-bits if I fill the nonce and the Nothing-up-my-sleeve numbers with key material?

As I studied, Salsa20/Chacha20 is basically a hash function that accepts a 64-byte input and returns a output of the same size of input. 128-bits of the input are filled with four "Nothing-up-my-...
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How can a generate a key with defined key size with a hash function with its security/internal state shorter than the key?

Let's suppose I took a high resolution photo full of entropy and I want to convert in a key with 2048-bits of security. Practically all the known hash algorithms have maximum 512-bits of security. Is ...
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Hashing 64-bit counters with different keys and XORing to blocks of plaintext, multiple times: Some questions

Let's suppose I want a 2048-bit block encryption. I take a 512-bit hash funcion (as Blake2b), provide a counter and a key and hash the counter and so XOR the hashed value in a ciphertext block, and ...
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Questions: Argon2, its internal state and security of it when generating keys larger than 256/512 bits

Let's suppose I want to use a cipher with a large key size, such as ISAAC that supports 8192 bits ogf key. I can hash with sha-256 or sha-512 and iterate until reaches the key size but I won't get ...
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How are cryptographic tokens and secret keys different?

Can someone throw light on the differences between tokens and secret keys? I understand that "tokens" are crypto artefacts "introduced" into a system by an external party in order ...
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When are PRNG used and when are CSPRNG used

I understand that PRNG are Random Number Generators that uses a deterministic algorithm based off of a seed. I also understand that CSRNG are PRNG that are cryptographic-ally safe to use for ...
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How are the keys used in cryptography generated?

It seems there are keys everywhere in cryptography. From things like HMAC to encryption (both asymmetric and symmetric). The bit I do not totally understand now is how are cryptographic keys generated?...
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How to interpret my professor's statement about "seed" and "symmetric-key encryption"?

In the cryptography course, the professor said that: these days for symmetric key encryption, instead of sending out the key, Alice sends the seed to Bob, and then based on that Bob can get the key. ...
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Vigenere Decryption with key length

I have a question. If I have 2 ciphertexts given and the same key has been used on both. They key lenght is the same as the plaintext and cipherrtext length. How do I decrypt them and find the key. So ...
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How to decompose a public key into subgroups EC?

Is it possible to decompose the public key into its own subgroups? Suppose we know the order P with which the public key was generated ...
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How to get a common coordinate from two different coordinates on Elliptic Curves? [duplicate]

I am trying to write a SageMath script that multiplies two coordinates on Elliptic Curves into one common coordinate. SageMath Elliptic curves over finite fields ...
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