Encryption is the process of transforming plaintext using a cipher into ciphertext to make it unreadable to anyone except those possessing the key. Decryption is the process of transforming that ciphertext back into plaintext, using the key.

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Decoding Base64 encoded password with internal hashing

This is complicated, please bear with me. I was given a username and encoded password list to decode. The list came from an export function of Cyberoam firewall (physical device), and was a .csv ...
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1answer
38 views

Which one these alternatives using authentication and encryption will solve this multiple-user database problem?

Which one these alternatives using authentication and encryption will solve this multiple-user database problem ? I'm trying to understand the field of cryptography, so I've started reading a ...
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29 views

Encryption of plain text using stream cipher algorithm

We know that in stream cipher algorithms plain text and generated key are Xored byte by byte. Generated key depends on how much plain text there is and on that basis key will generate and plain text ...
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1answer
21 views

What is the signifcance of inside threat in “How to Construct Multicast Cryptosystems … Secure Against CCA2”

In How to Construct Multicast Cryptosystems Provably Secure Against Adaptive Chosen Ciphertext Attack, the paper states under preliminaries: We consider the scenario where a single party, called ...
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1answer
73 views

Super-simple encryption of short strings

I want to anonymise the initials of experiment participants by giving each a pseudonymic set of initials, by encrypting their true initials. Their initials are only two or three letters in length. ...
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1answer
70 views

Decrypting an encrypted text file

I have encrypted a text file which contains few lines of text. After performing the encryption process, the encrypted text is saved into a text file. The Cipher text for the word "Inform" is "24 102 ...
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1answer
54 views

AES encryption only taking 32 bits [on hold]

The code I have below is in AutoIT. The problem I have with the code is that it can only encrypt 32 bits at a time. How do I make it encrypt an indefinite number of bits (or at least 128)? ...
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172 views

Is it possible to break enigma code with a todays laptop

I have a 500 characters enigma encoded text. Random rollers were used (not the ones from wikipedia). I know of this flaw. I can guess some words that sould be in the text, but this probably doesn't ...
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41 views

Rabin cryptosystem with 1 mod 4

We have p and q which are distinct primes congruent to 1 mod 4. Then we have n = p*q. Do you know any algorith for calculating square roots for the decryption in this case? I'm asking for some ...
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2answers
44 views

Are there drawbacks to encrypting data locally before being encrypted in cloud backup (multiple encryption)?

I am planning on backing up my hard drive using a cloud backup service but have become skeptical of the industry based on incidents like these: ...
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28 views

Winmain Error on Cygwin [on hold]

I am running some C code, i have not made this code but from the comments the code seems to work. For the code to work i have saved a header file than compiled the code. I keep getting this error ...
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1answer
532 views

Why does applying 56-bit DES twice only give 57 bits of security? [duplicate]

Given two 56-bit keys, $k_1$ and $k_2$, why does $E_{k_1}(E_{k_2}(M))$ only give 57 bits of security? So basically I'm unsure why it only gives 57 bits of security; I understand that one key will ...
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44 views

What are the links between Cryptography and Algebraic Topology?

I have asked "What are application of Cryptography in Algebraic Topology". But I want to know whether are there any relation between Algebraic Topology and Cryptography. Are there any application of ...
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0answers
37 views

suitable method for encryption and decryption [closed]

I want to encrypt and store important data in mysql so that no one else can access its original form and I want to decrypt those data whenever required. Which encryption scheme is suitable for this ...
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1answer
42 views

What type of encryption is this? [closed]

I need to know what type of encrpytion is this, ed6467d63c907d220447b00bf875e4e017702ff5
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1answer
38 views

Is authentication length always a subset of encryption length?

Do in all the use cases, if I have to encrypt and authenticate, encrypt-then-authenticate or authenticate-then-encrypt, like in IPSEC, SSL or SSH or others, if I were to do these operations to a ...
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0answers
46 views

Why is the call to RSA_generate_key_ex() failing sometimes? [closed]

I'm trying to randomly generate a pair of RSA asymmetric keys, however with my current implementation, the RSA_generate_key_ex() method seems to hang forever. I'm unable to extract an error code ...
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0answers
18 views

Does it make sense to have multiple values of authentication and cipher offsets while encrypting a packet?

Consider a packet with N segments. cofsset(cipher offset - from where one must cipher) lies in arbitrary Segment "A". aoffset (authentication offset - from where one must authenticate) lies in ...
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0answers
274 views

RSA encrypted in logarithm. Is it right or wrong? [closed]

Factorization and primality test of Lepore-Santo in log [(Y-X)/6]+1 I will show you the basic example, that i sto say the factorization of two prime numbers because reterating this process we can ...
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0answers
125 views

Is chaotic encryption secure?

I know this sounds too broad. But I noticed that there was a chapter on chaotic crypto in the recent Handbook of Information and Communication Security Editors: Stavroulakis, Peter, Stamp, Mark (Eds.) ...
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1answer
72 views

Benefit of using random key in Shamir's Secret Sharing

I am implementing Shamir's Secret Sharing, and I find that in (t,n)-threshold scheme, the shares are just using 1,2,3...,n as the key to form the shares ...
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0answers
46 views

Why is plain ElGamal not secure?

Why is plain ElGamal not secure? What is the proof behind it?
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1answer
84 views

How does the Blowfish algorithm key initialization work

I'm having some trouble understanding the Blowfish encryption algorithm. From the Wikipedia article... The secret key is then, byte by byte, cycling the key if necessary, XORed with all the ...
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0answers
85 views

Axolotl ratchet crypto protocol in plain English [closed]

I have been trying to read and understand https://github.com/trevp/axolotl/wiki but there's too much technical wording which I can't understand. From what other developers tell me it's the safest ...
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66 views
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1answer
61 views

How to encrypt a vector $e\in Z^{m}$ using LWE

I have a vector $e \in Z^{m}$, now I want to encrypt it by using LWE (Learning With Errors). Because in LWE, we have to encrypt of a bit $\{0,1\}$. How can I encrypt a vector $e \in Z^{m}$? Thank you ...
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1answer
101 views

Encrypt entire payload or only confidential parts of payload?

In cases where a large complex data structure contains elements that are a mix of confidential and not-so-confidential data, what would be the pros & cons of: encrypting the entire structure ...
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1answer
73 views

Creating a random password based off of a prime number

So I am making an application that basically creates strings that must be encrypted before they are stored on a user's device. If the user blindly starts running the application without creating a ...
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1answer
55 views

How does the certificate authority generate a signature F?

E=encrypt(K,M) - is message M encrypted with key K gives encrypted text E M=decrypt(K,E) - is encrypted text E decrypted with key K gives message M KCA−pub,KCA−priv - is the private-public key pair ...
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1answer
118 views

Decrypted RSA 64 bit encryption using modulus and private exponent. Got gobbledygook [Verify] [closed]

As part of an experiment, I was given a .enc RSA (encrypted) file that was most likely generated using openssl. I had the public key, I factored it, obtained the private exponent, and decrypted the ...
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1answer
154 views

How to decrypt a '.enc' file that has been encrypted with RSA using a public key?

While solving a CTF challenge online, I came across a situation where I needed to decrypt a '.enc' file that has been encrypted using someone's public key. The ...
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1answer
29 views

DSA: Authentication and assurance of authorized parties

When dealing with Asymmetric cryptographic algorithms, usually the sender of the critical data asks the listener for a Public Key for encrypting the data and sending them. This is while the private ...
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3answers
78 views

Is the keystream transmitted with the ciphertext when a stream cipher is used?

When a stream cipher is used and a keystream is generated to be XOR'ed with the plaintext, is the keystream sent with the ciphertext so that the receiver knows how to decrypt it? Or does the ...
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1answer
110 views

Is there a need to encrypt data when send over https? [closed]

I was monitoring web traffic from my Android mobile using Man in the middle proxy. I installed certificate signed from my server in my mobile and I could see all applications sending sensitive ...
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73 views

In what countries am I now allowed to talk about technical details of cryptography? [closed]

I hope this is the correct place to post this, otherwise I'm sorry. The OpenSSL Legality section states: OR EVEN JUST COMMUNICATING TECHNICAL DETAILS ABOUT CRYPTOGRAPHY SOFTWARE IS ILLEGAL IN ...
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16 views

how do i encrypt a user input using shared secret and then decrypt it using ECDH? [migrated]

i am using diffie helman key exchange method. i have got the keys and shared secret. however now am unable to encrypt the user input and generate the cypher text. any suggestions? my code till now is ...
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1answer
94 views

How to encypt/decrypt messages after ECDH key agreement

I am using Diffie-Helman key exchange to generate the shared secret. But how will can a message be encrypted using this shared key?
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1answer
331 views

What are the vulnerabilities of this homemade encryption algorithm?

I decided to program a relatively trivial encryption algorithm in my downtime. This algorithm takes a seed from a user (supports floating point seeds), and then adds 1 to the seed for every iteration ...
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1answer
156 views

Is it safe to encrypt random data using ECB mode?

If I have 48 random bytes, is it safe to encrypt them using ECB mode? Or is there still a good reason to use another mode like CTR, CBC, etc.? Context is this: I am creating something like a TLS ...
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0answers
22 views

Device intercommunication with commands

I want to create a smart house project, and in that i bought some simple RF modules. Those modules don't support crypto out of the box but i want to connect them to a device that i would program to ...
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1answer
209 views

Cryptography system by combining a block cipher and a stream cipher

I have to come up with a design for a cryptography system by combining a block cipher and a stream cipher. I can't seem to come up with anything on my own. Can someone point me in the right direction ...
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2answers
125 views

Prove that if we redefine the key space, we can assume Gen chooses a key uniformly

I am working on problem 2.1 in Introduction to Modern Cryptography 2nd edition by Katz and Lindell. 2.1) Prove that by redefining the key space, we may assume that the key generation algorithm ...
2
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1answer
86 views

Stacked LFSR - why not used?

New to cryptographic, weak in math. I have designed a PRG which consist of 33 LFSR's, each 32 bits wide. I use one of the LFSR's as "selector", using the 5 LSB from this register to select one of ...
2
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1answer
961 views

Practical brute-force attack on 128 bit encryption

In brute-force attack calculations cryptographers say we should assume an attacker will find the key after $2^{(n/2)}$ tries. If n=128, then n/2=64. We know that this is practical (A 64 bit key is ...
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1answer
54 views

Key sizes supported by 3DES

I read about 3DES encryption but I don't understand exactly what the specific meaning of key size is. For example I found that 3DES supports 64, 128, 192, and 256 bits key size. What are all the ...
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0answers
46 views

common ways / methods to try to break a SP network

I have a very little cryptography background (but a relatively solid maths background) so my below question is very general. Basically I have been given a SP network with an output to reverse. I ...
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1answer
78 views

NTRU Encryption

It's using Euclidian inverse. Can you show it step by step? $$N=7, q=11, a = 3+2X^2 -3X^4 +X^6$$ the inverse of $a \pmod {11}$ is $$A=-2+4X+2X^2 +4X^3 -4X^4 +2X^5 -2X^6$$ How do we compute $A$?
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1answer
93 views

Are modes of operation algorithms practical?

I took a cryptography class back in college, and now that I am working my 1st career one of the things currently on my plate is coming up with an algorithm to encrypt data before it's placed on the ...
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1answer
91 views

Is it safe to use PBEWithMD5AndDES?

I'm encrypting some of my (not so much important) files with PBEWithMD5AndDES. Is it a strong method or it can be de-crypt easily without knowing my selected ...
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1answer
63 views

How are RSA and ElGamal compatible in PGP?

I'm starting to play with PGP and I don't understand how if your key pair is RSA you can encrypt a message for someone whose key is for example ElGamal. How does the asymmetric key exchange work if ...