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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What is the main difference between a key, an IV and a nonce?
What are the main differences between a nonce, a key and an IV? Without any doubt the key should be kept secret. But what about the nonce and the IV? What's the main difference between them and their ...
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How to find modulus from a RSA public key?
I am studying the RSA cryptosystem. The public key consists of $(n, e)$, the modulus (product of two large primes), and the encryption exponent. I want to separate the modulus $n$ and exponent $e$. A ...
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Differences between the terms "pre-master secret", "master secret", "private key", and "shared secret"?
Both crypto.SE and security.SE have excellent Q&As about how TLS generates session keys (I have linked some at the bottom).
In reading these threads I'm having troubles with terminology since the ...
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Why do all SSH-RSA Keys begin with "AAAAB3NzaC1yc"?
My friend and I have been generating a few SSH2 RSA keys and noticed all the public keys begin with AAAAB3NzaC1yc, with the similarity extending to ...
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Can I remove newlines in a public key?
Can I remove new lines from the RSA public key file to get a one line string? So the question is if the key looks like this
AAA
BBB
CCC
or
...
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Where and how to store private keys in web applications for private messaging with web browsers
I am working on a web application enabling users to communicate over private messages which is just one part of the whole system. The main focus during my development process is to protect the privacy ...
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What is the practical impact of using System.Random which is not cryptographically random?
I recently noticed a .NET software using PBKDF to derive an encryption key from a password string. This password string was ...
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Using the same RSA keypair to sign and encrypt
The RSA signature operation is basically the same as encrypting with the private key. In particular, both operations use the same kind of keys.
Is it safe to use the same RSA keypair both for ...
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When using Curve25519, why does the private key always have a fixed bit at 2^254?
When using Curve25519, the private key always seems to have a fixed bit set at position $2^{254}$.
Why is that? Is there any good reason to use a fixed positioned most-significant-bit in the private ...
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How can SSL secure a two-way communication with only one key-pair?
As I understand it, SSL involved the use of a public-private key pair. How does this enable two-way communication?
Suppose I have some server with which I wish to communicate securely. I connect to ...
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Key derivation functions (KDF): What are they, what are their main purposes and how they can be used?
What are KDFs? What are their main purposes? How they can be used, in other words, what's their drill in a cryptography scheme?
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Can a hard drive store clear text data that is physically impossible to retrieve?
I'm trying to study how HSM and TPM works when storing secret data in clear text. How can they achieve physical impossibility in retrieving secret data?
I get the point in software, if you just have ...
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How many RSA keys before a collision?
I was wondering how many possible private/public keys exist? If a million people – for whatever reason – would try to generate 5 keys each in the same minute (on the same date and time) is there a ...
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Related-key attacks on AES
According to Wikipedia:
Related-key attacks can break AES-192 and AES-256 with complexities $2^{176}$ and $2^{99.5}$, respectively.
What are the requirements for these attacks (i.e how many ...
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Why does PBKDF2 xor the iterations of the hash function together?
The definition of PBKDF2 states that I obtain a derived key (1) by calling a pseudorandom function a bunch of times recursively:
$U_1 = PRF(password, salt)$
$U_2 = PRF(password, U_1)$
…
$U_n = PRF(...
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Is a PRG more costly than AES or any other encryption standard?
I know that there are many encryption standards that take a key and sometimes an IV to produce a cipher-text (the most prominent one is AES). These standards usually involve many rounds of addition ...
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Why do Feistel ciphers need round keys?
Looking at the design for Feistel ciphers, they use a list of round keys which are generated from the main key using the key schedule of the associated block cipher. Some block ciphers need this as to ...
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Are all possible EC private keys valid?
I usually generate a key pair using OpenSSL or Bouncy Castle.
I'm using curve secp256k1.
The 256bit private keys look fairly random.
Do all values of "private ...
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If PGP and GPG both follow the OpenPGP standard, are they 100% compatible in all use cases?
If someone gives me their PGP key, can I use it with GPG, and vice versa, all the time (100% interchangeable)? Or are there times when they are not compatible, when only PGP can be used with a PGP key,...
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Can we ensure the security of a crypto-algorithm and -implementaton against acoustic cryptanalysis?
Like people always say: “Attacks only get worse…” — which is why I'm asking early.
I have been reading the paper “RSA Key Extraction via Low-Bandwidth Acoustic Cryptanalysis” published December 18, ...
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Where do I securely store the key for a system where the source is visible?
I have a customer with an Access database (ugh!) in which credit cards are stored in plaintext (yikes!), so amongst other changes I'm doing in the app, I'm applying some encryption in there.
I've ...
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How exactly does key whitening manage to increase security?
Wikipedia states that key whitening increases security:
In cryptography, key whitening is a technique intended to increase the security of an iterated block cipher. It consists of steps that combine ...
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Relation between Key-exchange and Public-Key encryption schemes
Recently we have seen a lot of papers on Post-quantum key-establishment (key encapsulation mechanism or Key-exchange), largely due to the standardization call of NIST for PQ-protocols. However, most ...
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RSA private key integrity check
I am working on a device whose OS provides an RSA Private primitive, where the inputs are the message, and the usual components of a private key. Unfortunately it is bugged so that in some cases of ...
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What is the difference between key size and block size (for AES)?
We are working on AES and want to develop a website which should provide an encryption facility but we are not understanding the difference between key and the block size. More appropriately what does ...
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Do I need to worry about timing attacks in Base64 encoding/decoding of private keys?
Do I need to worry about timing attacks in Base64 encoding/decoding of private keys? This is a common operation (ex. PEM keys) and is variable time in typical implementations.
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Two different keys decrypting same content
is there some generally available algorithm which will encrypt a short string and generate two unique keys so that any of the two can be used to decrypt the message again? It doesn't has to be "super ...
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AES key reuse and guessing the key
Bit of a noob question and a fair bit of Googling didn't help. I understand that the current encryption standard is AES256. A few questions
Is the point of this (and other encryption techniques) to ...
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Can curve25519 keys be used with ed25519 keys?
Can curve25519 keys be used with ed25519?
I'd prefer to use ed25519, but there isn't a fast java version. For my application, I'd like to use curve25519 until I can get a faster ed25519 for java.
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Why do crypto tools display key components in such an unusual format?
openssl x509 (v1.0.1f) displays public key moduli as arrays of hex-encoded bytes, 15 columns wide, starting with a leading 00::
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What is the largest performed/possible bruteforce attack to date?
I've read that cracking 128-bit key is currently out of reach of all humanity. However, I can't seem to find any information on what scope of brute force attacks have been performed or are possible at ...
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If Kerckhoff's Principle holds, why do we need a cipher at all?
I understand Kerckhoff's principle, in a very practical sense, that the best attack that can be performed on a given cryptographic algorithm should be only as practical, if not less practical, than an ...
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1 Billion Bit Encryption?
So, browsing through YouTube, I stumbled on this video interview of John Draper (Captain Crunch), one of the first "hackers". He talks for about 3 minutes (until 27:48) about his home rolled ...
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How does GPG verify succesful decryption?
How does GPG (or other programs using the OpenPGP file format) verify that it has succeeded with decryption (for symmetrically encrypted data)?
Is something appended to the clear text so there exist ...
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What's the most secure way to derive a key from a password repeatably?
I'm trying to write a cloud storage application where everything the user uploads is unreadable by the server, encrypted client-side before being sent.
Currently, the flow looks like this:
User ...
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Offline Group Key Agreement - Cross Device Syncing
I have a specific use case I am interested in. I have spent the better part of the night reading research papers. I am beginning to believe what I want is not possible so I wanted to confirm here.
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Why does OpenSSL differentiate between PSS and non-PSS for private key generation?
RSA-PSS private keys
The following command will generate an RSA-PSS private key:
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How and why can a decryption program tell me that a key is incorrect?
I have noticed that some programs used for file encryption will tell you if an entered key is wrong when you try to decrypt. It seems (to me at least) that this would mean that the key somehow is ...
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How to calculate an IV when I have a shared private key?
I'm working with a server/client system that has securely negotiated a private key. I need to encrypt/decrypt messages passing in both directions which are typically between 100 bytes to 100 KB. I'm ...
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How strong are Bitlocker recovery keys?
This is an example of a bitlocker recovery key;
820042-335825-646573-481530-265253-688132-339900-822810
İs that key actually strong? It does not have any letters, ...
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What is a related key?
We talk of related keys and related key attacks, but what is a 'related key'? So in three related parts:-
How can one key be related to another key?
Is there a metric describing the degree of ...
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Why in cryptographic schemes we always assume that the key and plaintext are independent?
Why do we always assume in cryptographic schemes that the key and plaintext are independent? What if the plaintext depends on the key? How can this endanger security? Is this assumption essential for ...
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WhatsApp end-to-end encryption
WhatsApp offers end-to-end encryption. However, when I start using it on a second device such as a PC running Windows, I can decrypt incoming messages without providing any private key into my second ...
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How long should a HMAC cryptographic key be?
In the top answer to this question the answerer says 'with a sufficently long key'.
I am using a SHA1-HMAC (may switch to SHA256-HMAC) algorithm to verify cookies sent to clients as authentication ...
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For a given plaintext-ciphertext pair, how many valid AES keys are there?
For $PT\in \mathbb{M}$ and $CT\in \mathbb{C}$, let $\mathbb{F}=\{f|f:\mathbb{M}\rightarrow\mathbb{C}\}$ be the collection of all functions from $\mathbb{M}$ to $\mathbb{C}$. Then AES encryption under ...
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HMAC-SHA-512 with a 256-bit key
I am implementing hmac-sha-512 in an integrated system. However, one subsystem is only supports the use of 256-bit keys.
I read in https://www.rfc-editor.org/rfc/rfc4868 that:
However, note that [...
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Why is the Keyspace of a Substitution Cipher not 2^26 but 2^88
It is known that a cipher has a keyspace of cryptographic algorithm whose key length is $n$ is given by $2^n$, but the keyspace of the substitution cipher is $2^{88}$ which is an approximation of $26!$...
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Encrypt a file once with 50 characters password or twice with 25 characters?
What better Encrypt the file once with 50 characters password or encrypt it twice each time with 25 characters password.
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AES 256 Encryption - Is it really easy to decrypt if you have the key?
So this might sound like a crazy question but bear with me for a minute. I can't find any info on the internet and so am here, although this might have been a good place to start.
I've recently ...
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DES — Can I recover the key when I have both ciphertext and the plaintext?
Given a message and DES encrypted form of said message, is it possible to efficiently compute the key used to encrypt the data?
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