Questions tagged [key-derivation]

In cryptography, a key derivation function (or KDF) derives one or more secret keys from a secret value such as a master key or other known information such as a password or passphrase using a pseudo-random function. Keyed cryptographic hash functions are popular examples of pseudo-random functions used for key derivation.

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BIP32 Extended Key to EC Private and Public Key Pair

We are working on an application in Android using Java. In our project, we used to generate EC key pairs (of size 384 bits) using SpongyCastle - an old Android version of Bouncy Castle. The problem ...
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Doubts regarding implementing AES-128 bit algorithm in my IOT system

I want to implement AES-128 in my IoT network which consists of a Master device which runs Linux on it and slave devices which are 8-bit micro-controllers that periodically transmit data packets to ...
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Scrypt cipher - known vulnerabilities and cryptanalysis? [duplicate]

there is a Scrypt cipher which is used for exmaple by some cryptos like LItecoin for their mining algorithm. I never heared of scrypt. I know eg SHA256 which is well analyzed and considered as secure ...
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Group membership with unique anonymous claims

Is it possible to accomplish the following scheme? There is a Server (S) and many clients. Each client enrolls with S, exposing its real identity; S saves the real identity information in its ...
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Multiple AES Key Derivation from a master key

I need cryptography advice regarding this issue. Kamus is a service that encrypts secrets for applications running on Kubernetes. When using AES (actually, Rijndael) symmetric encryption, Kamus uses ...
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Multiple random keys vs multiple keys derived from master key

If Alice is going to share a symmetric encryption key and a kmac key with Bob using asymmetric encryption (sign with static key, encrypt with ephemeral keys - an authenticated KEM), what are the ...
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Why does NIST SP 800 `KDF in Counter Mode' specification require a PRF rather than a PRP?

This is the NIST SP 800 KDF in Counter Mode specification. Where $K_I$ is the input key, $[i]_2$ is the counter value, Label and Context are fixed-length strings and $[L]_2$ is the output size, the ...
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ZKA Approval Scheme

I'm having hard time finding any resources for ZKA (Zentraler Kreditausschuss Approval) security schematics used by IFSF Part 3-21 Security Standard (https://ifsf.org/documents/ifsf-standards/). ...
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“Safe” or Safest Method for Non-Hardened Key Derivation Functionality

I'm currently working on the development of an unorthodox system in which, ideally, there would be one master key pair, with thousands of keys derived from it. There needs to be a way to prove that ...
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Is using AES-256 with a key of less than 256 bits of entropy still quantum-resistant?

Encrypting with AES-256 is widely claimed to be post-quantum secure. But let's take a case where you use an initial key that has less than 256 bits of real entropy. In this example, let's work with a ...
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Securely derive AES and ED25519 keys from a ED25519 seed

Go's ed25519 package exposes a function which allows creating a private key from a 32 byte seed. See: https://godoc.org/golang.org/x/crypto/ed25519#NewKeyFromSeed The reason I want to use this is ...
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aeskeygenassist with only one imm8

I'm analyzing a binary which for its AES encryption, its only calling aeskeygenassist once and for the last argument (imm8, the ...
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Why RSA-KEM is more secure than Textbook-RSA?

I am studying RSA-KEM but I can not see why it should be as secure as padding RSA messages (e.g with RSA-OAEP) when exchanging a key between two parties (say A and B). It is easy to see that Textbook-...
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Key-Agreement & Key-Transport for Symmetric Authentication System

Question: I want to know what kind of Master Key sharing process is pursuit on Symmetric encryption environments (strictly symmetric, also in the key sharing scheme). As I am aware there are several ...
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Would XOR'ing two Argon2 keys add extra security?

When a user registers on the app, they need to provide a password they create and we provide them with a randomly generated passphrase (e.g. Apple Cat Ladder Fire). We then use Libsodium's ...
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memory-hard KDF that's just a giant permutation?

Why aren't there memory-hard KDF functions that simply build a 1GB permutation and permute it? Then hash the 1GB result. For example, use a hash function (unfixed output mode) on the key+salt and use ...
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Why use PBKDF2 over SHA-512 to derive AES encryption key? [duplicate]

Suppose I am using user passwords to derive AES-128-CBC encryption key. This key will be used to encrypt some sensitive data for the user so that even the website owner / operator can not decrypt it. ...
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ECDH security when no KDF is used

Let's suppose our device performs ECDH with a fixed, unknown, private key $\text{prv}$. It accepts as input any point $Q$ lying in the proper subgroup of the proper elliptic curve, then computes: $P =...
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Given a hash function; assuming domain % codomain = 0 and uniform collision distribution; how is entropy lost by collisions (not output truncation)?

Assuming our domain and codomain both have 4 elements, the uniform distribution of inputs to outputs means the function is injective. It is widely agreed that randomly selecting a domain element ...
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Proof of shared secret through key derivation

Alice gives a random key $K$ (e.g. 32 bytes long) to Bob through a secure channel. Bob want to prove to Alice through an unsecured channel that he knows the key. Is it secure for Bob to send $s||KDF(...
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Entropy preservation through cryptographic hash function

Background First, while studying MinEntropy a bit, I came across an NIST paper, "DRAFT SP 800-90B (second draft)," which suggests "twice" the entropy of the underlying block of a cryptographic hash ...
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NIST SP800-108 KDF modes comparison

According to NIST SP800-108, there are three modes that can build KDF from PRF: counter mode, feedback mode and double-pipeline iteration mode. Assume that the same PRF and input distribution are used,...
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Optimal memory-hard KDF parameters when faced with small, slow memory

I am developing for a low-power embedded system. It has two ARM9 processors at 48 MHz each. One of the processors has access to 6 MiB of "fast" memory as well as access to 26 MiB of "slow" memory. The ...
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Is there more than one public key for a private key?

Does deriving the public key from an RSA private key always yield the same result? And if so, does this generally apply to all asymmetric cryptosystems?
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Split hash for 2 keys

These are the steps: Hash ECDH shared secret with SHA3-512 Concatenate odd bytes and rehash with SHA3-512 for AES-256 key Concatenate even bytes and rehash with SHA3-512 for KMAC key Is this key ...
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Key derivation scheme with shared secrets?

I want to derive a list of sub-keys derived[t] from a master key mk by a key derivation function ...
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Password hashing security of argon2 versus bcrypt/PBKDF2?

I wonder if it can be approximated how much of a security margin the new argon2 hash, winner of the password hashing competition, can give over bcrypt or PBKDF2, for an attacker using large GPU ...
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Are there any known problems or attacks for using SHA1(AES_key) as the HMAC key?

See this answer that explains the following sequence of operations: CipherText = IV|| AES(key1,iv,message) tag = hmac(key2,ciphertext) That answer says, You ...
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Station-to-Station protocol questions

Basic Station-to-Station protocol which authenticates Bob and Alice if they safely shared their long-term asymmetric public keys. Alice sends Bob her public key $A_K$ Bob receives $A_K$ and computes ...
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PHP AES-256 CBC faster than AES-128 CBC?

For the last couple of days, I have been learning a bit about encrypting data in PHP, as I need a good encryption/decryption function for storing users' passwords in a DB. I use ...
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Why cryptsetup default KDF is PBKDF2 and not Argon2(id)?

I plan to do a clean install of ArchLinux with Full Disk Encryption (with LUKS) but I'm not sure to understand the default KDF choice (PBKDF2+SHA-256). I didn't manage to find any pieces of evidence ...
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RSA Modulus doesn't match the primes [closed]

I generated a 2048-bit RSA key with ssh-keygen. When running: openssl rsa -in key -noout -text The result is: ...
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Which risks are associated with deriving multiple keys from the same DH secret Z?

NIST recommends Krawczyk's HMAC-based key derivation function (HKDF) in SP-800-56C (PDF). HKDF shall e.g. be used to create keys from shared secrets after Diffie Hellman key establishment. NIST ...
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Security implications of using a high entropy password with a low iteration count for a key derivation function

This question is related to my other question, but also this entropy calculation question as well as this article about PBKDF2. It may also be considered as a duplicate of this question, although in ...
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Key derivation on Arduino

The ATmega2560 is slow - it's a single core, 16MHz 8-bit AVR. Despite that, I need to use some encryption on it, and since it is limited to a few blocks, AES-256 can be used. However, the key ...
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Rekeying procedure - how “far” from bijection?

Imagine that I want to change the key in order to prevent side-channel attacks on key and to protect against big load on the one key. It is desirable that key change procedure would look like random ...
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Are two keys derived from the same password vulnerable to a related key attack?

Background I am currently writing a password manager application. As usual, the passwords are put in a file encrypted using a user-entered password. I'm using the NaCl library but actually it's not ...
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Is bcrypt better than GnuPG's iterated+salted hashing method?

GnuPG has slow hash built-in in form of iterated+salted S2K. Does it have disadvantages in comparison with bcrypt or scrypt? Is GnuPG's slow hash method easily automated in GPUs?
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What exactly does s2k do in gpg

So I recently discovered the --s2k mode in gpg. Sadly it is not very well-documented. I mean, what is ...
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Should we run PBKDF2 for every plaintext to be protected or should we run PBKDF2 only once?

I am going to store secrets from users. The secrets need to be stored confidentially. For this question, I am concerned only with confidentiality (not integrity). Here is how my encryption scheme is: ...
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Is deriving the IV from the password secure?

I came across an encryption scheme to encrypt files with AES-256. You can see the initialization of the decryption routine below: ...
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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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Can you derive a 128 bit AES encryption key using PBKDF2 with SHA-256

I got confused about key derivation functions. For my project, I need to derive a 128 bits AES encryption key in CTR mode. To do so, I'm using a PBKDF2 to derive this encryption key using an initial ...
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Is it problematic to use PBKDF2-HMAC-SHA256 to derive a 512-bit XTS key?

PBKDF2 should only be used to generate a larger output than the hash function it uses if the output is used in such a way that it has a flat keyspace. As far as I am aware, XTS does not have a flat ...
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Are two halves of PBKDF output “related” [duplicate]

In other words, in the context of authenticated encryption using Encrypt-Then-MAC, is this stupid?: ...
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Use a SHA256 as a key for AES256

Is it safe to use the SHA256 of a hard-to-bruteforce string as the key to encrypt data with AES256?
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What is a randomly derived key?

It is a well-known fact that using the same key + nonce combination with a stream cipher twice breaks security. The NaCl library has different primitives for authenticated encryption (i.e., ...
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KDF based on X9.63 vs. NIST SP800-108

What is the difference between KDF based on NIST SP800-108 vs. the older one in ANSI X9.63? When should one be selected over the other? Thanks.
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“Dave Check” for a tweakable P-256 ECDH KDF

I have two devices with hardware tokens that contain P-256 private keys, and which allow me to compute ECDH shared secrets with arbitrary public keys. I need to build a tweakable key derivation ...
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Is it safe to reuse the salt for generating symmetric keys for a chat application?

I'm writing a program that allows two users to communicate over E2E encrypted chat with a secret they have agreed upon in the past. The process works as follows: A key is derived from the secret ...