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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Key stream instead of key schedule

Let's consider block cipher in CTR mode. And let's consider keyed PRNG or just good PRNG with seed as a key. PRNG has to be very fast. Is it a good idea to put away key schedule and do "infinite&...
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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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Can SHA256 hash be considered as a secure key proof?

I want to use PBKDF2 with 1,000,000 iterations (I don't know yet exactly how many I will choose) to derive a 256-bit symmetric key K from a password provided by a user (at least 40 bits of entropy). ...
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Is it possible to increase the encryption security of a short key?

If I encrypt a file with a short 4 digit pin is there any way to make it more secure. I've thought about hashing the 4 digit pin and using the result as the encryption key. I think this would work as ...
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key length considerations

Learning about cryptosystems and basic cryptology and I have a sort of vague understanding of key sizes/key space and think I may have done something wrong in my calculations, can someone please ...
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CNG/BCrypt/NCrypt Import an ephemeral AES key wrapped with a persistent RSA key

I will write some kind of security client/server pair: The server part provides wrapped AES keys. The client part, based on CNG win32 API (ncrypt.h+...
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AES Password Based Key Derivation Iterations

I have been writing my own implementation of the Advanced Encryption Standard with cipher block chaining in python3 for the last several months, mimicking the OpenSSL command line interface. I can ...
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How much data can we encrypt using AES 256 before changing the key?

Although this question has been answered in this link (After How Much Data Encryption (AES-256) we should change key?), I am not satisfied with the answers because the Recommendation for Block Cipher ...
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How do I encrypt a bunch of messages by different authors, shared with that group of people?

I'm still getting my head around public/private key cryptography, and I can't quite work out how to ask the right question to get an answer for this problem, but here goes! Alice, Bob, Carol, and ...
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How Secure Is Splitting A Bitcoin Private Key?

NOTE: This question cannot be posted to Bitcoin SE because it will not render there due to the mathematical notation. Since the mathematical notation is part of the question, this is the more ...
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Using same key pairs in several different encryption tools and version

can we use the same key pairs created by an encryption tool, for encryption decryption, in another encryption tool ? for ex, created by hypercrypt, but being used in cryptermite, or maybe within the ...
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Decrypt the same ciphertext to multiple messages of my choice if I can use any key I want to decrypt

In a modern secure encryption scheme, is it possible(both theoretically and practically) to encrypt a message using a key to get the following ciphertext c = Enc(M1,k1) and later find another key so ...
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127 views

How are ECC keys stored?

I am trying to figure out what typical formats and sizes, etc. are, for storing ECC public and private keys. Some quick research turned up X9.62 (to which I don't have access) and SEC1. But then there ...
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Randomizing output of HKDF for the same input key material [duplicate]

Given HKDF and a master input material key $k$, I would like to derive ephemeral keys that cannot be linked together. If I understand correctly, the specification of $HKDF$ adding a unique random $...
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Is PyCryptodome's export_key with passphrase secure?

When exporting a private key with PyCryptodome, DER format, PKCS#8 and a suitably strong passphrase, is the resulting exported key secure enough to place somewhere that you would not normally want ...
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How do I multiply two points on an elliptic curve?

Tell me if there is a way to multiply two points on an elliptic curve? For example, as in secp256k1 ...
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87 views

Proving I can solve an equation without disclosing the solution (zero-knowledge proof)

Given a (potentially multivariable) equation $f(x)=0$, Peggy wants to prove to Victor that she knows a solution $x^\star$ to it without actually disclosing anything information about the value of $x^\...
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RSA key requirements so that it can decrypt a DES key

I came upon a solved exercise that uses a client's RSA key to encrypt a DES key. It has the following phrase: value of n for RSA key generation has been chosen accordingly so that the DES key can be ...
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Does a man-in-the-middle attack apply in this scenario?

Disclaimer: I am aware that the question's title does not adequately describe what I am asking, but it is the best I could come up with. Any improvement is welcome. I am a university student studying ...
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118 views

How to calculate number of possible key pairs in RSA

What determines the number of possible RSA key pairs for a given $n$? Is it because $\varphi(n)$ produces the number of values that are less than $n$ and coprime with $n$? Is it as simple as $\varphi(...
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Unilateral authentication with implicit key authentication

Is it possible to design a cryptography protocol with achieving unilateral authentication of one party A by party B using implicit key authentication? Key authentication is the property whereby one ...
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Is there a secure way of allowing users of my app to selectively share data from an external service?

Is there a secure way of allowing users of my app to selectively share data from an external service with my app? In order for the users of my app to get their personal data from the external service ...
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Finding the private key for this signature scheme

Assume the signature scheme where $x$ is the private key and the public key $y = g^x \pmod{p}$. The signature works as: Choose $h \in \{0, \dots, p-2 \}$ s.t.: $\mathcal{H}(m) + x + h \equiv 0 \pmod{...
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Fast irreversible transformation/compression of short messages using a secret

I'm looking for a very fast function $f(m, k) $ that takes a 64-bit integer $m$ and a fixed secret key $k$ of virtually any size (generated by a CSPRNG) and turns them into a 64- or 32-bit integer $ r ...
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Modifying SubBytes Operation In AES

Let us assume the SubBytes operation changed to just shift right operation. for example - f(00011101) = 10001110 How we perform a Known/ Chosen Plaintext Attack and find the key? How much time does it ...
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Encrypting multiple groups of data with separate keys in a single encrypted column

I will write this question using a database example, but please note this detail may be irrelevant. Let's say I have data belonging to N clients stored in a single column of a database table. Each ...
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Post-quantum asymmetric encryption algorithms

One could use Falcon-512 for establishing a private and public key for an asymmetric context. Whereas in a symmetric context, we could use firesaber/saber/variants in order to obtain a shared secret ...
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Key storage management of session keys and long term keys

In key management, one of the topics is key storage, I want to know where and how these keys(long-term and short-term) are stored? For example I read that android password apps use KeyStore api to ...
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Identity verification code

I'm looking for a service that can verify an identity by enter a code or key. For example, I want to be able to send a doc to a anonymous person with a specify code or crypto and that person copy that ...
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66 views

Symmetric Exchange Key Sharing

Question: Suppose that there are 10000 = 10^4 banks and 10 payment card organisations (PCOs). How many secret keys will be needed if each PCO shares a unique secret key with each bank? How many extra ...
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How to know which key was used for an AES encryption?

I am starting a project where several categories of sensitive data have to be accessed within a table. Based on his role, a user can see clear text columns (not encrypted), accessible columns (...
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Can private key used in ECDSA be discovered when many signatures were colleced? [duplicate]

Can private key used in ECDSA be discovered when many signatures of different messages were collected (1M+) or may signatures of the same message were collected? Will small nonce bias be easily ...
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Probability of false positive key matching two plaintext/ciphertext pairs

Given a keyspace of $ 2^{80} $ and plaintext space of $2^{64}$. And two plaintext and ciphertext pairs $(x_1, y_1)$ , $(x_2, y_2)$. Now we have $2^{80}/2^{64} = 2^{16}$ keys that encrypt $x_1$ to $y_1$...
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How to be able to change the password to access data encrypted with AES-GCM, without reencrypting?

Let's say you need to encrypt plaintext which is 1 TB big. You have a password pwd. This very classical AES-GCM process is ...
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What would be the most recommended AES && RSA Keys for production?

While I am a front-end developer and not a security expert programmer, I am worry about the keys I am using for my AES && RSA encryption. Please help me to understand: Is the following keys ...
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What is the importance of AES add round Key (K0)?

A high-level overview of AES is according to Wikipedia Key expansion; Initial round key addition; 9, 11, or 13 rounds; Final round (making 10, 12, or 14 rounds in total). I can understand all the ...
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105 views

DES security if used a SHA3 function instead of Normal DES function?

I was practicing some python programming and I decided to implement a simple DES encryption function, so i decided to take some shortcuts so instead of DES expansion boxes and s-Boxes i just used a ...
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Is there a “two of three keys needed” encryption?

Sorry if this question is stupid, but is there an encryption algorithm where a message is encrypted with a set of n keys which can then be deciphered with any sufficiently large subset of those? E.g. ...
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Help needed for IBM KCV

I found old key letters used in EFT HSMs with TDES keys, parted in two halfs. The check value printed on this letters is called IBM CV and doubled IBM CV. My newer HSM does not support this kind of ...
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129 views

Using a public key as a secret to authenticate the sender

Question I have a scenario where a public key is exchanged out-of-band with exactly one person $A$ and is later used in a key-exchange scheme with $A$. Is knowledge of the public key (i.e., producing ...
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71 views

Calculating symmetric key bit strength

16 byte key where each byte is in range 0-255, generated using cryptograhic PRNG will be believed to have 128 bit strength. What would be a bit strength of a key generated using same quality PRNG, ...
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Secret sharing by using just “private secrets”?

TLS is using 3 way handshake. Isn't that possible to use such 3 way handshake protocol to share a secret without using a public key scheme, for instance as follows: Let A, B be private secrets of ...
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Splitting Secret Key

If I split a key $k$ into three pieces as $k1, k2$ and $k3$ how should I distribute the keys among three people such that any two of them are able to evaluate PRF, but be secure from any one of them ...

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