# All Questions

19,125 questions
11 views

### Encrypt UDP packet with time-generated encryption key

I'd like you to help me solve a dilemma of mine. I am currently building a home automation from scratch for my next house. The basic gist of it is that I will send UDP packets over a local network. ...
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### Prime number size and RSA decryption

Is there a former proof for why larger prime numbers make RSA securer? Maybe a theorem to show that it takes much more time to find out the private key if primes are larger?
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### Pollard's Kangaroo— What is the failure probability (assuming random functions)?

I'm reading Pollard's paper on solving the discrete log problem, i.e. to find $x$ given $y = g^x$, where $g$ is a generator of the group. He has a Kangaroo Algorithm (page 4) which allows you, if you ...
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### CRT to decrypt RSA [on hold]

How can the Chinese Remainder Theorem be used to decrypt RSA (or the public key) and find out the private key? If it is possible to do this with the CRT, then does the size of prime numbers used to ...
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### Why adversary'' and challenger'' and what are typical roles of those?

I'm confused with words adversary and challenger, that are used in proof of security of some cryptosystems. For example, adversary and challenger appear in the formal definitions of IND-CPA, IND-CCA, ...
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### Does this have a valid purpose [on hold]

2muchcoffee Just invented this. At the moment it is a pen and paper cipher. It is a cipher where you can store a file on a hard drive or U.SB. that has been encrypted by an unlimited number of ...
108 views

### Yarrow and weak cryptographic keys on macOS

Given that macOS uses Yarrow as a PRNG, and Yarrow is only capable of 160 bit outputs (/dev/random on macOS is actually Yarrow) are keys generated on macOS weaker than Linux? Even BSD has switched to ...
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### Why does a padding block exist for ECB and CBC modes?

In ECB and CBC mode, the size of cipher text is more than the plain-text size by one padding block. From what I read, ECB does a simple encryption to each 64 bit block of a Plain text, and produces ...
31 views

### Chinese remainder theorem

Z/11Z[X] is the finite field P(2) = 4 P(3) = 3 P(5) = 7 How can I solve my congruence system with polynoms? I made my system of congruence like that : X = 2 [4] X = 3 [3] X = 5 [7] And it gives me ...
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### Are one time pads still secure when using randomly generated words as the pad?

I was researching the US military's DIANA one-time-pad system and came across the following quote purportedly from a former US Special Forces soldier: Special Forces were one of (if not the only) ...
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### What's the safest way to encrypt a messenger application?

How can I safely encrypt a messenger application that sends data over the Internet via TCP? I've already taken a look at Salsa20, but I don't know if that's a good algorithm to use for this. What ...
236 views

### Examples of protocols that are insecure when run concurrently

I was reading Canetti00 Universally Composable security paper. The first page of introduction says that there are some MPC protocols and Zero knowledge protocols that are insecure under concurrent ...
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### Signature verification vs decryption?

I've found this explanation regarding signature verification but I still confused In the example in the picture, the sender sign the hash using his secret key. The output of signing produces a ...
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### How to use openssl securely?

I don't want openssl to log my keys and passwords... but I don't use gpg as I need more manual control for my purpose. I also don't like gpg and would like to use openssl without logging. Does ...
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### What does “simulatable” mean in security proofs?

I am reading a security proof in a paper as follows. Regarding the data confidentiality of users, all related public transcripts are simply the ciphertexts $\mathcal{C}_1,\ldots,\mathcal{C}_n$. The ...
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### What does it imply if in RSA pow(m, e, n) is same as the m

So, Let's assume we have n which is made up of 2 strong primes which cannot be factored & e which is textbook value of e ...
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### Mixing Cipher Lower Bounds

Let Z be a cipher system consisting of three m-sequence linear feedback shift registers (LFSR) of length 128 bits each which are assumed to be not cryptographically secure and the registers are seeded ...
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### Hardwired secret key in public/ private key encryption

I am new to cryptography and I need to know some details about the hardwired keys. Taking as an example multi-input functional encryption 1, a key is hardwired in the description of the key ...