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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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How is key rotation defined?

I'm aware that it's advisable to rotate cryptographic keys periodically. HKDF accepts high-entropy input (IKM - Input Key Material), and expands it to an arbitrary length. It also accepts a salt, ...
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Is it possible to successfully encrypt/decrypt in DUKPT using different sized BDKs?

We are having our P2PE Solution validated against the PCI P2PE standard. We currently use a TDEA 2-key based BDK, and IPEK in both the encryption and decryption environments. ANSI X9.24-1 (2009) ...
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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, ...
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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 ...
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50 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 ...
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How do i manage encryption keys with a cloud provider?

I would like to provision services from a Software as a Service (SaaS) provider. This is multitenant environment (multiple companies will be using a single instance of the application, with a single ...
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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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533 views

How can I find or reverse engineer the whitening in an AES algorithm?

I am working with this black box cryptography scheme. I know the plain text, cipher text, and everything else except how they whiten the data (or key?). Everything is 128 bit, 16 bytes. I have two ...
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Anonymisation resilient to key leak

Problem statement Elbonian citizens have been issued a card holding a random $B_j\in\{0,1\}^b$, $0\le j<2^n$, $b\ge n+20$ (representative example $b=64$, $n=28$). The habit has grown to use this ...
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Alternative way to provision secret in Intel SGX enclave

I have a case where I have multiple clients(non sgx, assumeed safe) and server(sgx based), talking over a network. I wanted to provision shared (per client) key which is used to encrypt and decrypt ...
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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 ...
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GPG Sub Key Renewal Questions

Last year, I followed this guide to create two GnuPG Smart Cards; one card with the Primary Key and the other card with the Sub-keys. I noticed that the sub keys were close to expiring so I renewed ...
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RSA - find d,e with restrictions

For academic purposes, assuming $n, p, q$ with $n\approx 2^{4096}$ and $p,q\approx 2^{2048}$. I need to find ($e,d$) such that: $e$ is smaller than $2^{64}$ $d\approx 2^{4096}$ and will have as ...
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Does the length of the keyword used for keytable for Playfair matter?

So for Playfair, we choose a keyword and put that in the keytable with no duplicates. Then, we fill the rest of the table with alphabets in order that are not in the keyword without 'J'. Does the ...
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Generating interactive, secure multiple ECC key pairs deterministically

In Elliptic Curve Cryptography (ECC) assuming user A has a private public key pair of $S$, $P$ accordingly with generator point $G$ which as we know is: $$P=S*G$$ Assuming that user A wants to ...
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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: ...
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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, ...
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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; ...
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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 ...
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Nature of risk(s) from KeeChallenge XML file stored in cloud at Onedrive

As a noob user of KeePass2 on Windows desktop and Keypass2Android on my phone, supplemented by YubiKey Neo configured for hmac-sha1 challenge response, I noticed that Keepass2Android appears to store ...
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Is there hierarchical key generation that completely tolerates leakage?

Is there a hierarchical key construction algorithm that achieves forward/backward privacy with any (unlimited) leakage of private non-master keys? What I mean is that if there's an unbounded number ...
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Where shoul I store private/public keys and how should I share it?

I'm new in terms of encryption and I have to encrypt the data between two Java Spring applications, one have serves as MVC framework and other as Web Service, I'm implementing an asymmetric encryption ...
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How does the authd protocol work?

So far, I have been able to research on what it is: authentication; authorization; using resource authd. I still have not come across a definitive answer or ...
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MAC with key supplied afterwards

Looking at HMAC and KMAC it seems that the key is always required up front, i.e. before starting to process any other data. However, in many protocols the key may not be known it advance. For instance,...
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Question on recovering a key in the algorithm

Let $E$ be a block cipher that has block size and key size both equal to 64 bits. Let $E'$ be a block cipher that has 64-bit block size and is defined as follows: For a 128 bits key $K \mathbin\Vert ...
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See the RSA's $n = p q, e \text{ and } d$ from ssh-keygen

For learning purposes, how to get the RSA's parameters (I use standard notation): $n = p q $, where $p$ and $q$ are prime and $e$, $d$, such that $ed = 1 \ (mod\ \varphi (n)) $ when doing ...
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Cracking a key using a combination of partial keys

As part of a cryptanalytic attack I've carried out, I used a divide-and-conquer strategy to divide the secret key $k$ into several equal-sized partial keys $k = {k_1, k_2, ...}$. The attack works ...
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How can I split a packed Ed25519 public signing key into its X and Y coordinates?

I'm using the Curve25519 code (from http://www.dlbeer.co.nz/oss/c25519.html), and trying to convert from a public signing key (Edwards form) to a public key-exchange key (Montgomery form). There's ...
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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.
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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 ...
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162 views

Handling key invalidation

I'm writing an Android app which will need to store some data for the user as a byte array of unknown length. The data must be encrypted. I have gone down the path of the hardware-backed keystore and ...
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What is the use of key iterations?

I read about PBKDF2 on Wikipedia and seen few apps. having option to manually enter number of iterations. I am still not clear on this. (1) With what I understood, key iterations can be used only ...
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Deriving Minimum Description Length of Substitution Key

Given a plaintext: Now is the time for all good men to come to the aid of their country because the quick brown fox jumped over the lazy dog. and a substitution ciphertext: Mpe od yjr yo,r ...
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Confidentiality then Integrity with different keys

Can anyone describe how we can do what is said in the below sentence which is in Mark Stamp crypto slides (PPTX) on slide number 101 : Can do a little better - about 1.5 “encryptions” The whole ...
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Keys and key-stretching when authenticating requests?

I'm making a REST application and still a bit confused about this issue. basically, to authenticate incoming requests, I give out userId, issued timestamp, expiry timestamp (normally 3 months after ...
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52 views

cumulative secrets

Imagine a server with an authentication scheme that utilizes an element of randomness in new sessions (i.e. one that uses the secure remote password protocol). At the end of a successful ...
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Hiding the identity of a party within the Kerberos authentication scheme

In the Kerberos authentication protocol, as described here: would it be safer to replace step (1) with: $$ A \rightarrow T : A, E_{K_A{_{T}}}(B, N_A) $$ so that a passive adversary does not know ...
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exchanging private key between service and iPhone app - digital signing

I need to do digital signing of my request data which will be sent to the server. My server sends distinct private keys to her clients after authentication and expects all responses to be digitally ...
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Hill cipher key space

Key space is the set of all possible keys that can be used to generate a key. We using the number of valid key to describe it. I've given a hill cipher of block size $k$ over alphabet of size $p$, ...
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Random numbers for Master Key and Key_block

Exploration through RFCs concludes that random numbers used in the creation of Master Key and Key Block(Key material for Encryption Key and Mac Secret) are from ServerHello.random and ClientHello....
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IV and Headers inside cipher text

I am a bit confused about the use of IV, and key hash. Is the key hash and IV stored inside the headers of the cipher text? Isn't it a security risk to store this header information? By key hash I ...
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can permutation matrix be found in parallel processing technique?

Let us say there exists a permutation matrix $n \times n$ for some large $n$. Then, there are $n!$ possible permutations. If one to use brute-force to find the secret permutation among $n!$ ...
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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 ...
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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 ...
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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 ...
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JWK vs. raw for key wrapping

Context (TLDR below) So I’m developing an application that uses a high-iteration-count PBKDF2 algorithm to derive a symmetric AES-GCM key from a user-provided (enforced to be reasonably strong) ...
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MTI/A0: modular arithmetic or elliptic curves?

In the Handbook of Applied Cryptography (Menezes, A. J.; van Oorschot, P. C. & Vanstone, S. A.) Protocol MTI/A0 key agreement (algorithm 12.53) described as $\mod p$-protocol. The survey Overview ...
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Minmum Key Length for Block Ciphers Required keeping in view futuristic quantum computers

In an answer to the Question "What are recommended, general strategies to start block-cipher design and/or analysis?", in terms of brute force attack, it is written 256 bits is considered secure ...
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key hierarchy management and master key

I have this equation, $E_{K_{as}}(E_{K_{bs}}(K_{ab}))$ which means $K_{ab}$ is encrypted by $K_{bs}$ then whole packet is encrypted by $K_{as}$. I think the key structure is $K_{as}$ is the master ...
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Can we use more than one irreducible polynomial in AES?

I understand that the irr. poly is used to form the s-box (and inv. s-box), the key schedule and the mix columns. But could we use a different irr. poly for the mix columns and another for the key ...