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Crypto

Questions about Blake2x: Its state size (internal state) and its security when generating keys with size more than 256/512bits

phantomcraft

4/20/23, 3:21 PM

I read the Blake2x paper: https://www.blake2.net/blake2x.pdf

It says Blake2x can be used to build a "DRBG" (CSPRNG): https://csrc.nist.gov/glossary/term/deterministic_random_bit_generator

"An algorithm that produces a sequence of bits that are uniquely determined from an initial value called a seed. The output of the DRBG “appears” to be random, i.e., the output is statistically indistinguishable from random values. A cryptographic DRBG has the additional property that the output is unpredictable, given that the seed is not known. A DRBG is sometimes also called a Pseudo Random Number Generator (PRNG) or a deterministic random number generator."

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I want to know if the initial state (state size) of Blake2x is "enlarged" when hashing, because I didn't understand this notation:

Despite the internal state of Blake be 256/512 bits, can Blake2x be used to build a stream cipher (CSPRNG/DRBG) with security more than 256/512 bits given a seed with a larger size?

If I have a source full of entropy (like a high resolution photo) and I hash with Blake2x to a key of 8192 bits per example, will I get a key material with this size?

Can some Blake2 enthusiast answer my questions? (I tried to contact one of Blake2x authors, Jean-Philippe Aumasson, but I gave no response).

0 + 0

random-number-generator

key-size

key-generation

blake2

poncho

4/20/23, 3:23 PM

Why do you care about "more than 256 bit security"? Does your attack model include adversaries that can harness the entire output of the sun to attack your cipher?

kelalaka

4/20/23, 3:34 PM

are you considering this key size for the PQ-PKC?

phantomcraft

4/20/23, 11:06 PM

@poncho I want to keep my secrets forever, I hold material about secret societies.

phantomcraft

4/20/23, 11:07 PM

@kelalaka I want to write a disk encryption program that will use keys sizes like this.

kelalaka

4/20/23, 11:14 PM

https://crypto.stackexchange.com/q/1145/18298

phantomcraft

4/21/23, 1:09 AM

@kelalaka /\ I already read this topic, but I'm paranoid and I want my secrets safe forever.

poncho

4/21/23, 1:11 AM

So, how are you going to protect the key? You can't hope to memorize it, and if you store it anywhere, someone could steal it...

phantomcraft

4/21/23, 1:44 AM

I store the key in a microSD card and hide, if I die, other person who I asked will destroy it.

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Questions about Blake2x: Its state size (internal state) and its security when generating keys with size more than 256/512bits

TH: คำถามเกี่ยวกับ Blake2x: ขนาดสถานะ (สถานะภายใน) และความปลอดภัยเมื่อสร้างคีย์ที่มีขนาดมากกว่า 256/512 บิต

RO: Întrebări despre Blake2x: dimensiunea stării sale (starea internă) și securitatea sa atunci când generează chei cu dimensiunea mai mare de 256/512 biți

RU: Вопросы о Blake2x: размер его состояния (внутреннее состояние) и его безопасность при генерации ключей размером более 256/512 бит.

VI: Câu hỏi về Blake2x: Kích thước trạng thái (trạng thái bên trong) và tính bảo mật của nó khi tạo khóa có kích thước lớn hơn 256/512bit

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