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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Public key stored in PKI [closed]

In a public key infrastructure how does a User A communicate with the user B? How does user A send his public key to user B ? Where is a public key stored where do they retrieve it from? This question ...
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Cryptographic Key Management system [closed]

A multinational company has five regional offices around the globe, between which large amounts of confidential data are exchanged every day over the internal network. It also maintains a separate web ...
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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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What are the vulnerabilities in this algorithm?

Bob and Alice sets common keys for a and b variables. All variables are equal length. Every message x and y variables are randomly changes ...
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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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Block cipher design criteria when specifying key size

For a given block size of N bits, the total number of possible permutations is (2^N)! In order to select from any one of the possible permutations, the key would have to be of length log2((2^N)!) ...
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How to decide if an element is a public key in NTRU encryption scheme?

First, I'm using the settings of https://en.wikipedia.org/wiki/NTRUEncrypt, with $L_f$ set of polynomials with $d_f+1$ coefficients equal to 1, $d_f$ equal to $-1$ and the remaining $N-2d_f-1$ equal ...
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Is Keystore a file, a database, a specification?

What exactly are keystores? I understand they are used to store things like private keys, certificates etc. But how exactly is that done? Is it just an encrypted databases where you put all these ...
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Rivest Cipher 6 (RC6) Key Scheduler

I am trying to understand the Key Scheduler used in RC6 and I have a total of 3 questions. The RC6 Wikipedia page says that the only difference between the RC5 and RC6 key scheduler is that more words ...
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Is it safe to use the same seed phrase for different cryptocurrency protocols

I want to use the same seed phrase for severl cryptocoins (Bticoin, Ethereum, Nano, etc.). I understand that each protocol has its own phrase length and possibly a different way of generating the ...
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Encoding salt as hex before hashing bad practice?

I was reading a question about symmetric keys here and found the answer quite interesting. It mentions: Be sure to pass in the raw bytes, and not, e.g., a hex-encoded string Can someone elaborate on ...
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How To Read Encryption/Hashing Notation

This is very basic, but what I'm wondering is: I have a few notations of hashing/RSA encryption that I'm unsure of when reading. PKE(PW, K) With PW representing a password, K representing a 128-bit ...
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If a Pseudorandom Function (PRF) is supplied with a key with the same size of output block, can 2 or more keys generate the same output for a input?

There a 2 examples: A block cipher with 128 bits of block size taking a plaintext and a 128 bits key (AES-128). A keyed hash function with 1024 bits of block size in its output, taking a message and a ...
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Number of Legitimate Bitcoin Wallets from unsequenced set of 24 Words

If someone found a scrambled BIP-39 24 word sequence how hard would it be to determine the correct sequence that yields someone's wallet. Are there multiple different unique sequences of the same 24 ...
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Can an arbitrary physical image be a key?

Assume an arbitrary secret physical image¹, such as a privately made chemical Polaroid™ similar to this Is there a feasible and secure way that this physical image could be used as cryptographic key, ...
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Encryption of data with multiple possible decryption keys

I'm new to the Cryptography Stack Exchange, so my question might be very naive. What encryption algorithms are out there that will allow different decryption keys to decrypt the same piece of ...
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Designing your own Algorithm

I have been told to design my own algorithm as a college assignment. What I could have come up with was a random cipher. For example: Suppose my plaintext is: AND ...
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CBC mode, fixed Key and IV but unique plaintexts

My transport channel is sufficiently tiny that I don't want to give up 16 bytes for an IV (AES block size). My environment is also resource constrained such that I have no RNG. I have read over and ...
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decryption in IDEA if the encryption was made without the output transformation

I'm implementing IDEA encryption and decryption and I'm trying to implement it in different variants(e.g if we didn't do the output transformation or if we don't do full 8-round encryption). I got the ...
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Secret key expiration

I am looking for suitable techniques through which secret keys can be expired after a certain time limit. Is there any such method in cryptography?
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What are the explicit usage of different keys derived from SKEYSEED in IKE?

We have seven different keys derived from DH key and nonces via PRF in IKEv2 as skd, skai, skar, skei, sker, skpi, skpr. Why different keys are generated for initator and responder for encryption? ...
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Is PRF XORed with its key still a PRF? (always)

$\forall k \in \{0,1\}^n,m \in \mathbb{M},F_k(m)$ is defined as follows: $F_k(m) = F'_k(m) \oplus k$. It is known that $F'_k$ is a PRF. Note: 𝕄 is the message space and it's assumed that the key $k$ ...
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How to protect a non-extractable Secret Key in indexedDB?

I have encrypted data in AES-GCM with the crypto API. The initialisation vector is then ...
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Domain Keys Identified Mail (DKIM)

If a company uses Domain Keys Identified Mail ("sender adds a special signature which includes author name / date signed by RSA Private Key. Receiver verifies the signature by looking up the ...
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How to generate keys from a 56 bit using DES

First I just want to apologize for my lack of knowledge in this system. The professor kind of gave us an exercise to solve before even going through the lessons. I tired to look at videos online but ...
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Why is it not possible to attack an AES by creating a function to model the substitution that occurs in a s-box?

I realise that s boxes are able to make the transformations done in AES non-linear. However I am unsure how this makes AES secure. For instance if we had no s box then it is possible to calculate the ...
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CrypTool RSA Features [duplicate]

I am attempting to manually encrypt a plaintext message (message = MI) using RSA. I receive an answer of: 33,264 and 21,164. When I enter the same plaintext into CrypTool to confirm that my ...
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Am I Doing RSA Correctly?

I am trying to figure out how to complete RSA manually. I am trying to encode a simple block message (Mi). I used CrypTool to determine the encryption. When I "manually" computed the ...
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Key stream instead of key schedule

Let's consider a block cipher in CTR mode. And let's consider a keyed PRNG or just a good PRNG with a seed as the key. The PRNG has to be very fast. Is it a good idea to put away the key schedule and ...
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Online AES Calculator

I am currently looking into how AES works and found a calculator online: http://testprotect.com/appendix/AEScalc I understand that the AES process has 10 rounds of calculations. Does this mean that ...
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Why is this DES key considered weak?

I understand the premise of weak keys in DES and cryptography. From searching online, I understand that keys that are comprised of all zeroes / all ones / alternating ones and zeroes / alternating ...
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Why do you need to apply hash over DH shared key? [duplicate]

I`ve read multiple times that it is not safe to use the shared key resulted from DH key exchange directly and that you need to do a KDF or hash over it and then use the result as a key. Why is it not ...
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How does a forward search attack work? [duplicate]

I just came across this term “forward search attack” while reading about Interchange key and Session key. The book mentioned that using session key helps to prevent attacks such as forward search ...
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Equivalent keys in Hash Functions

Let's suppose I want to use a (keyed) hash function as a stream cipher, I provide a key and a message to be hashed as a counter (like a nonce), and so, XOR each hashed output block on the plaintext. ...
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Assistance with Permutation Cipher (Columnar Transposition) [closed]

I was wondering if someone could provide some assistance with understanding a permutation cipher. I have both the cipher text as well as the plaintext but am having some difficulties trying to find ...
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Is using /dev/hwrng for raw key material secure?

Is using /dev/hwrng for raw key material secure (as long as you trust the hardware)? I tested it using the rngtest tool and it has good output.
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Are there any cryptographic algorithms, which lets the user apply some modifications on the encoded data, without decoding it?

I would like to encode some data with a key, and send it to a third party. They don't know the key to decode it, but I would like to make it possible for them to apply some modifications on it. Then ...

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