Stack Exchange Network

Stack Exchange network consists of 175 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.

-1
votes
0answers
16 views

How do I revoke aws smtp oauth token2 on iPhone [on hold]

How do I revoke oauth 2 tokens and phishing emails
0
votes
2answers
40 views

How is EC key encoded in PKCS#8?

I just started working with certificates and signatures. For an application I write I need a key pair for ECDSA signatures, using the elliptic curve secp384r1 (aka NIST P-384). I produced such a key ...
3
votes
3answers
79 views

How to generate a good symmetric secret key

I would like to generate a good secret key, that later will be used to encrypt data symmetrically. I am not sure how to generate a good secret key. I use Linux, I am not sure which sources of ...
1
vote
0answers
51 views

Guessing the key in AES256-GCM?

I assume that my case is weird but I've the following information: IV: 0x263e or 0x3e26 Auth tag: 0x25 AES256-GCM encrypted payload: 0x4eec96df534ade4c013a AES256-GCM decrypted payload: ...
0
votes
1answer
30 views

Problem in generation of keys in KP-ABE

In KP-ABE the owner encrypts the message using attributes say a'. The Attribute authority(AA) designs an access structure and implants that access structure in keys generated by AA for the user. So, ...
0
votes
0answers
19 views

Given cipher text, not given any plain text or key How do you find them [closed]

A Hill Cipher over the above 27-symbol alphabet was used to produce the ciphertext Use the same cipher with the same key to encrypt the string WCHURCHILL of length 10. Carefully enter the encrypted ...
0
votes
0answers
29 views

Aes brute force when part of data known [duplicate]

I have buffer of 16 bytes that encrypt with AES 128 cbc with IV =000000......(all IV is 0) I have the encrypted buffer, and I know 7 bytes from 16 bytes before the encryption , I dont know the key . ...
1
vote
0answers
55 views

Why derive keys from a master key instead of generating random keys?

I noticed AWS KMS generates encryption keys based off of a master key, using a key derivation function (HKDF). What's the practical advantage of deriving keys based on a master key? Isn't it simpler ...
0
votes
1answer
70 views

How 'safe' is a 12-digit alphanumeric key?

To Access my data over a Portal i got a 12-digit alphanumeric key like: VGW8-U98T-TXLV How safe is this key? I don't want to know the chance to win with brute force. I want to know there are several ...
0
votes
1answer
53 views

How to find a triple of keys that maps plaintext to given cipherext using EDE

What is a practical method for for finding a triple of keys that maps a given plaintext to a given ciphertext using EDE? I think this requires something similar to a man-in-the-middle attack...
0
votes
1answer
89 views

Encryption: am I doing it right?

I'm trying to get a per-user encryption key scheme off the ground and need some validation from wiser crypto pros. Consider the following procedure: User provides registration information to include ...
3
votes
2answers
91 views

Which hash is used when providing signature algorithm ED25519 or ED448?

From TLS 1.3 there are two signature algorithms using edDSA: /* EdDSA algorithms */ ed25519(0x0807), ed448(0x0808), All the other signature-...
2
votes
3answers
133 views

Low entropy - how does it compromise the crypto

One of the often pointed out mistake in dealing with crypto is not having enough entropy in the system. Without enough entropy the random numbers generated are not random enough. But what I am not ...
3
votes
1answer
66 views

Definition of symmetric cipher and definition of asymmetric cipher

So I'm currently taking a cryptography class right now and my professor has told the class that she can't even define symmetric cipher for us without getting into asymmetric ciphers and the textbook ...
4
votes
1answer
115 views

$\boxplus$- key addition vs $\oplus$- key addition

GOST cipher , Hight cipher and SEA cipher use key addition based on modular arithmetic addition (module key size $\boxplus$) compared to many ciphers which use arithmetic addition modulo 2 ( $\oplus$)....
0
votes
0answers
36 views

Chameleon hashes as encryption keys

I'm a newbie to cryptography and I have been wondering about the possibility of using Chameleon hashes as symmetric encryption keys. Here is my scenario and my thought process: Let us consider a ...
0
votes
0answers
71 views

Yukel's Sieve - Factorization of Numbers into a Square Sieve

https://www.youtube.com/watch?v=liTTGeitpGQ https://www.youtube.com/watch?v=2nOwgiweyqc https://www.youtube.com/watch?v=rGwFsOG27DQ I came across these videos explaining a pattern that is found in ...
3
votes
1answer
64 views

In NIST modulus and key size recommendations is `group` equivalent to modulus and `key` equivalent to exponent?

Looking at the following NIST recommendations for a discrete logarithm, for 2016-2030 and beyond they list 3072-bit number for the group and 256-bit for the ...
6
votes
0answers
65 views

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. ...
0
votes
1answer
49 views

What is the difference between static and dynamic tokens?

First, what is the difference between hardware and software tokens? Tokens are "what you have" for example a car key or a chipcard. This would be (I think) hardware tokens? But what are software ...
2
votes
1answer
48 views

Emphemeral key creation from a long term shared secret (without DH)

Assuming I cannot use DH scheme, and the long term key is known to both sides, is there a known algorithm / standard that defines how to derive a short term key from a long term key?
2
votes
1answer
50 views

The key size of an ideal block cipher

My understanding of an ideal block cipher is as follows: For a block cipher with block size $n$, there are $2^n$ possible plaintexts. The number of possible keys (mappings) would then be $2^n!$. ...
7
votes
1answer
76 views

How complex must round constants be to resist slide attacks?

A key schedule that generates round keys by XORing a round constant with the key is linear and can be vulnerable to related key attacks, but let's ignore that for now. Constants are necessary to avoid ...
5
votes
1answer
744 views

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 ...
1
vote
1answer
60 views

While using onetime encryption is it possible that one can deduce the key of a message if the contents of the message are already known?

Let's say we have a randomly encrypted message and I pasted the contents of that message on a blog for some reason I do not share the key. Would you be able to figure out the key? This is the ...
2
votes
2answers
79 views

Does libsodium sealed box leak key ids?

I am using python and libnacl, which is a libsodium wrapper, to develop an application where users can deposit encrypted data. Alice uses ...
1
vote
2answers
70 views

Why is a smaller value preferred for the public key in RSA?

For my practice implementation of the RSA cryptosystem I use a random value generation function such the value of public key e holds: The public exponent $e$ and the modulus $n$ should be $e<\phi(...
6
votes
1answer
143 views

How does Twofish avoid weak keys if it uses key-dependent S-boxes?

From section 7.2.2 of the Twofish paper, the four S-boxes for the 128-bit cipher are generated with: $$\begin{align} s_0(x) &= q_1[q_0[q_0[x] \oplus s_{0,0}] \oplus s_{1,0}]\\ s_1(x) &= q_0[...
1
vote
1answer
48 views

Key, plaintext block and ciphertext block permutations question

Question: If a cipher’s key size is $k$ bits and its block size is $b$ bits, how many possible keys are there, how many possible plaintext blocks are there, and how many possible ciphertext blocks are ...
10
votes
4answers
3k views

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 ...
0
votes
0answers
12 views

Production Ready Message Format Standart for Key agreements on top of XMPP

Greedings, I try to run group key agreements on top of XMPP thus I want somehow a production used message format for key agreement. As far I found theese: XEP-0384: OMEMO Encryption XEP-0102 But all ...
1
vote
0answers
45 views

PCI DSS requirement 3.5.3

3.5.3 Store secret and private keys used to encrypt/decrypt cardholder data in one (or more) of the following forms at all times: ............ As at least two full-length key components or key shares, ...
2
votes
2answers
21 views

Mutual keys protection/wrapping

Is there a known risk in having two keys wrapping each other? Let's say, an adversary has access to both AESkey1(key2) and AESkey2(key1). Does it make it much easier for him to recover the keys?
2
votes
0answers
41 views

Why would one split HKDF output into multiple parts instead of expanding it multiple times

Reading the implementation details of Signal's approach on double ratchet algorithm I noticed the following key derivation procedure for using AES-CBC with HMAC: HKDF is used (...) to generate 80 ...
1
vote
0answers
14 views

GlobalSign cert in Trusted root for Google Services shows Sha1. Security postures

"GlobalSign" certificate in Trusted Root Certification Authorities for Google Services shows Sha1. Security postures are different than just 2-3 yr ago. At my home, router bought 2016, networked; ...
3
votes
2answers
543 views

How much extra security does key wrapping provide?

Wikipedia says: Key Wrap. Key Wrap constructions are a class of symmetric encryption algorithms designed to encapsulate (encrypt) cryptographic key material. The Key Wrap algorithms are intended ...
0
votes
1answer
52 views

ED25519 Child Key Derivation

Let's say I generate a keypair for a user with go's ed25519 package: pub, private := ed25519.GenerateKey(nil) And I want to generate additional child keys as ...
1
vote
1answer
41 views

Attack vector difference when not allowing repetitions in BIP-39

We are using a 12-word scheme BIP-39 mnenemonic key generating scheme that creates an entropy of 128-bit that is then used to generate a seed that in turn derives a private key for the user. It ...
0
votes
1answer
158 views

Key Entropy meaning Help

Can anyone help me understand key entropy the mathematics behind it and the uses for it? I understand most of it but I just want to understand what does $\log 2$ do like if I do. $\log 128 / \log 2 = ...
2
votes
1answer
231 views

Does the public key and private key for WhatsApp only remain within a WhatsApp account

The world of cryptography is starting to really intrigue me admittedly. I initially hated it because it looked too hard Mathematically but now it looks cool :) Got a good question for the experts and ...
7
votes
1answer
161 views

How to find fixed points for DES weak keys

Can someone explain me this please I am a bit confused? It's from a texbook I am reading (block cipher companion) it says that: each weak key has $2^{32}$ fixed points $m$ where $\operatorname{...
0
votes
1answer
53 views

Does repeated xoring of the (same) key K lower the entropy of K?

If a symmetric encryption key $K$ has been generated by some recommended (NIST for example) RBG then we should have a key with high entropy. But if we xor other bit-strings (e.g. IVs, other keys, etc....
1
vote
0answers
11 views

Asymmetrical encryption with multiple sufficient key-pairs [duplicate]

I have the following requirement: There are N public/private RSA key pairs. The encrypted data must be decryptable by any of the private keys alone, but not by any other key. For encryption, the ...
16
votes
5answers
3k views

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, and produces a cipher-text (the most prominent one is AES). These standards usually involve many rounds of addition ...
1
vote
0answers
15 views

Asyncronous Rachet tree: How user movability is handled is the Rachet tree being recreated?

As I have read the latest state of art in group key agreement is the Asyncronous Rachet Tree. But in applications like IRC that exists high user movability (users join in ans leave the room). Is ...
-1
votes
1answer
79 views

Find $F(2x)$ from $F(x) = a^x \bmod p$

Given $F(x) = a^x \bmod p$, where $a$ is a primitive root of $p$, Is it possible to work out what $F(2x)$ or $F(3x)$, etc if you know what $F(x)$ is but not $x$. If you use $F(x)$ then $F(2x)$, etc ...
2
votes
1answer
37 views

mDP kay agreement protocol where z's are found on the step where the common key is generated?

Whilst I was studying the mDP protocol I came across into the following step: Group Key agreement: Each $U_i$ checks whether $z_1 \bigoplus ... \bigoplus z_n = 0$ and whether all signatures $\...
1
vote
1answer
160 views

Signal Sender Keys: Why it works and which is the common key at the end?

As I has read upon "WhatsUp Encryption Overview" when a client receives a sender message then it performs the following actions: Decomposes Sender Message to ...
7
votes
1answer
185 views

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://tools.ietf.org/html/rfc4868 that: However, note that [...
1
vote
2answers
44 views

Maximum number of possible keys for a fixed-length password?

I'm reviewing some information and possibilities regarding key space size following a unique password requirement, as it were. This particular requirement is a fixed-length password of 12 characters, ...