Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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.

0
votes
2answers
119 views

Key vs Algorithm when applied to Enigma

I've just been reading the Why should I make my cipher public? question and answers on this site. I understand Kerckhoffs's principle, but I'm unsure exactly how this applies to Enigma - i.e. where ...
2
votes
2answers
74 views

Is it possible to prove that I have half a key to decrypt file, to someone who has other half, without disclosing my part?

Is it possible to prove that I have half a key to decrypt file, to someone who has other half, without disclosing my part? Or better yet, could you suggest a place where I can read about solved and ...
4
votes
3answers
932 views

Re-encryption without knowing the secret

Which encryption algorithms could be used for the following scenario? A user stores a file encrypted by someone else Then the user is asked to re-encrypt the file with a new secret The user stays ...
0
votes
2answers
116 views

Amateur question: Constant two way cryptography

First of all, I would like to tell you guys that I'm a complete noob at cryptography in general, so please pardon any dumb stuff I may say. Well, I have used a lot of cryptography libraries in a ...
1
vote
1answer
111 views

Is there a block cipher mode that doesn't use the key input of the block cipher?

Is there a block cipher mode that does encryption and decryption without using the "key" input of the block cipher? I ask this because rekeying a block cipher can be an expensive process, and I ...
4
votes
1answer
234 views

Should AES-CMAC key cryptoperiod be affected by MAC truncation to avoid birthday-attacks?

Given a 128-bit key used for authentication based on AES-CMAC, the NIST 800-38B recommendations suggest at least two criteria for a good key cryptoperiod: after 'MaxInvalids' error messages the key ...
0
votes
1answer
288 views

Perfect secrecy with some considerartion

According to eavesdropping indistinguishability experiment $PrivK_{A,\Pi}^{eav}$ from page 34 of this book, I define $\varepsilon$-perfect secrecy as this($\varepsilon>0)$: For every adversary $A$ ...
13
votes
3answers
2k views

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 ...
0
votes
1answer
1k views

How to know the type of encryption method

If I have a program that take a string to give me the ciphertext, nothing stored, using the same keys. The ciphertext is a base64. Can I figure out the type of encryption by the amount of characters ...
4
votes
2answers
5k views

How exactly are public and private keys used to encrypt and the decrypt data?

In asymmetric encryption schemes, a public key is used by an outside source to encrypt data to be sent to the holder of the private key. It's my understanding that public keys are generated from the ...
5
votes
1answer
342 views

What is logical key hierarchy (LKH)?

The question "Virtual key generation in Logical Key Hierarchy" asks how specific keys are constructed in LKH. Since I haven't heard of it and it isn't immediately obvious (not even from the linked RFC)...
3
votes
3answers
978 views

Where to store sensitive keys in a device?

I am working on some security features that should be executed by the firmware of a consumer device whose communication to a server must be secure. Any exchange of data is based on symmetric ...
0
votes
1answer
222 views

Possible to identify cryptographic keys in non-random binary data?

From my understanding, a well-generated cryptographic key would be indistinguishable from randomly generated binary data. However, I also know that most cryptographic keys do not appear surrounded ...
5
votes
1answer
397 views

If the plaintext contains the key used to encrypt the ciphertext, is the ciphertext easier to decrypt?

I have a symmetric key which can be used to encrypt plaintext and decrypt the resulting ciphertext. I use it to encrypt a plaintext which is a copy of the aforementioned key. My adversary gets a copy ...
1
vote
1answer
149 views

Understanding an encryption technique algorithm

I have trouble understanding steps for Key set generation mentioned in an article titled as "An optimized encryption technique using an arbitrary matrix with probabilistic encryption". The steps are: ...
1
vote
1answer
111 views

FHMQV-C \sigma calculation - Full Dual Exponential Challenge Response (FDCR) signature schemes-

I'm studying the protocol FHMQV - C but I don't understand how two honest parties can reach the same value of $\sigma$. The paper that I'm studying is: https://eprint.iacr.org/2009/408.pdf. If you ...
0
votes
1answer
58 views

Key generation algorithm based on bytes in a drive [closed]

I am a novice cyber security student and thought of a way to generate a random cryptographic key. The algorithm works as follows: Get the size (in bytes) of every file in a directory (drills down ...
-1
votes
2answers
1k views

Retrieving the 3DES decryption key from plaintext and ciphertext?

I have a hex key that I want to decrypt with a 3DES key in mode ECB. For example: ...
1
vote
1answer
151 views

security for PRF when key is changed often

Here's the situation. Suppose I have a secure PRF $F$ and use $F$ in the following way: for equal size message $m_i$ in $\{m_j\}^{q}_{j=1}$( $q=poly(n)$, $n$ is security parameter ), randomly select $...
3
votes
1answer
688 views

Is there a way to find $a$ and $b$ keywords in an affine cipher when only ciphertext but no plaintext is known?

I know simple formulas like $$E(x) = (ax+b)\pmod n$$ where $E(x)$ stands for encryption, $$D(y)= z(y-b)\pmod n$$ where $D(y)$ stands for decryption, and $$ax==1\pmod n$$ Assuming someone gives ...
0
votes
2answers
581 views

Perfect secrecy with XOR & SHIFT?

I have read that XOR provides perfect secrecy, when the key is perfectly random. However it's technically hard to generate truly random numbers, especially on computers, so that is why people use AES, ...
1
vote
0answers
32 views

Specifications for key management

Does anyone know of any commonly accepted or standard specifications for languages, modelling, diagramming, etc. for specifying and describing the life cycle of keys in a system? Thanks.
4
votes
2answers
738 views

Brute-forcing Symmetric Keys

Random keys are often produced using high-quality random generators. Assuming a key produced for a symmetrical cipher, this means that the number of zeros and ones in the key will, on average, ...
0
votes
2answers
179 views

How could consumer level OTP + QKD over the internet ever be practical?

Please note, I am in no way questioning the future usefulness of quantum key distribution (QKD) in certain applications. I have no doubt it will prove useful for large banks, and in certain military ...
2
votes
2answers
401 views

Building index for Bloom filter using cryptographic hash functions

I want to apply this secure index scheme for my Bloom filter, i.e. to use secret keys to insert items into the filter. In the paper to insert a word $w$ to the Bloom filter, they use a set of $r$ keys ...
0
votes
2answers
476 views

Best approach for storing private key

I'm working on a web service application which uses a self signed certificate. I apologize up front if this turns to be a dumb question. When using openssl for generating private key, it reveals (as ...
3
votes
3answers
2k views

Can someone randomly guess the key to AES 256 bit encryption?

Is it possible that someone can randomly input a key to AES 256 bit encryption and it is correct? What are the chances of this happening? Is it even possible or not?
2
votes
1answer
104 views

Is there a method of encryption where you can't work out the key even with the encrypted and decrypted message?

I'm looking for a method of encryption that fulfills the following parameters: To still be able to display a result even if decrypted with the wrong key. If the encrypted and decrypted message is ...
2
votes
1answer
221 views

Would using two keys for Salsa20 or ChaCha increase security?

Would using the keys (as in two passes with a key each) increase security for Salsa20 or ChaCha stream ciphers increase security?
0
votes
3answers
72 views

can half of an encrypted photo be decrypted with the key?

if we have like some part of the encrypted picture,is it there any way that the picture can be decrypted. is there any specific algorithm that allows this. like can from 60 per cent of the encrypted ...
5
votes
3answers
450 views

One Time Pad Alphabet Size

I am building a simple one time pad system using a low-power microcontroller to XOR a stored key with an input string, and vice versa. Due to several internal factors, it's very preferable for the ...
4
votes
1answer
104 views

Why use a separate key for each file?

I'm trying to understand "Option 2: Using a Client-Side Master Key" from https://docs.aws.amazon.com/AmazonS3/latest/dev/UsingClientSideEncryption.html#client-side-encryption-client-side-master-key-...
3
votes
3answers
1k views

What if in AES-128 CBC, IV is very related to KEY? [duplicate]

while digging into some secured communication protocol, I noticed a usage of AES-128 CBC that raised my attention. In it, the IV is tightly coupled to the Key, being a xor of its values with the byte ...
4
votes
3answers
1k views

How to verify the AES Key?

I'm Encrypting the data using AES-128 bit Encryption. I need to check whether the key is correct at the receiver side. How can I do that? Suppose At the receiver The user is asked to enter the KEY ...
5
votes
1answer
633 views

How to use ECDH keypairs algorithm for encryption and decryption same like RSA keypairs without key agreement?

Is it possible to use ECDH key pairs (Public and private keys) for encryption and decryption like RSA key pairs in encryption and decryption. Say for example, if i have RSA key pairs then i could do ...
3
votes
1answer
277 views

Brute forcing an elliptic curve encrypted key

I've been reading about ECC, and what I've established so far (correct me if I'm wrong) is that: pubKey = privKey * G where G is some special point on the secp256k1 curve. Doesn't this mean we ...
0
votes
2answers
236 views

Difference b/w Hash function & Keyed Hash function? And HMAC with Matyas-Meyer-Oseas hash function

I am looking for hash functions. In this process i came across hash & keyed hash functions(HAMC). In which it uses some has function to generate MAC. And also Matyas-Meyer-Oseas hash function, ...
5
votes
1answer
496 views

Key management in Java + Remembering passwords

I'm new within the area of crypto so I apologise if I am bad at explaining this, or have misunderstood certain areas. I'm currently developing a Java Fx application which includes the use of a '...
7
votes
2answers
670 views

CBC variant: why encrypt the nonce with a different key?

I am a newbie at cryptography. I understand the CBC encryption, somewhat. You don't want to use the same "IV" for every message because then the ciphers are not very random. My question is regarding ...
6
votes
1answer
142 views

Generally accepted standard(s) for key managment?

I am using an application of which in its privacy policy it has been stated the they use generally accepted standards to protect data. They encrypt data on their servers. So, what is/are the "...
3
votes
1answer
282 views

How can I store asymmetric keys server-side, so that they are only readable by devices?

I am building a platform in which there is a central server & devices (computers). These computers hold the same keys pairs that correspond to specific resources (shared between devices), so that ...
12
votes
1answer
2k views

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:: ...
1
vote
0answers
63 views

Why does facebook uses two secrets to secure API

I am working on a public API for my personal forum. Concerning the authentification of the requests and responses I plan to hash the payloads with a secret, known to me and the API user, and send the ...
1
vote
2answers
459 views

Do I need different encryption and decryption algorithms for each key?

Is a different encryption and decryption algorithm used for every secret key, or can I use the same encryption and decryption algorithm for different keys?
0
votes
1answer
701 views

Hashing entropy to generate 256bit key?

I have a 256bit fully random entropy source from dices, which is probably not cryptographically secure. I have read that it's customary to take the hash of the entropy source in order to generate a ...
3
votes
3answers
144 views

Is a large random number cryptographically equivalent to the product of multiple smaller ones?

Say I create a 256-bit key by taking a random number between $0$ and $2^{256}-1$. Would it be cryptographically equivalent to generate $8$ numbers $r_1\dots r_8$ between $0$ and $31$, and combining ...
1
vote
1answer
88 views

Self Generating key encryption based [duplicate]

I was wondering someting : Doing a XOR with a fixed length key on txt files is not secure. Basically : My key is "abc" ...
2
votes
3answers
804 views

Where should I store the private key (RSA) in a web application?

My web application receives encrypted data from another server encrypted with RSA keys. Where should I store the private key (RSA) in a .NET web application (Windows)? It seems that putting in it in ...
1
vote
1answer
140 views

Explain: An NTRU key for a lattice of dimension $d$ has size only $O(d\log{d})$

The associated NTRU lattice is of dimension $d=2N$. The public and private key sizes are both of length $O(N)=O(d/2)=O(d)$. So where does the $d\log(d)$ appear? Thanks in advance.
13
votes
4answers
3k views

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 ...