Questions tagged [multiple-encryption]

Multiple encryption means encrypting a message two or more times using either the same, or a different algorithm.

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Can we sign and encrypt with RSA keys of both sender and receiver?

By using RSA encryption, it is possible to "encrypt" sign with sender's private key and then with receiver's public key, and decrypt with receiver's private key and then with sender's public ...
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Is multiple encryption with stream ciphers vulnerable to meet-in-the-middle attacks?

Let's suppose I encrypt something with a stream cipher (CSPRNG) two times using two 256-bit keys and different IVs. Will I get 512-bit encryption strength?
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Is multiple encryption with CTR mode vulnerable to meet-in-the-middle attacks?

Let's suppose I want to encrypt my disk partition with AES-256 in CTR mode 2 times using two different keys and IVs. Will I get 512 bits of encryption strength?
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What is the easiest cipher to use in designing double ciphers?

I want to make a double cipher consisting of two encryption method Enc1 and Enc2, and two corresponding decryption mechanisms Dec1 and Dec2. I want it so that: (1) we can encrypt any message M1 to a ...
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Encrypting multiple groups of data with separate keys in a single encrypted column

I will write this question using a database example, but please note this detail may be irrelevant. Let's say I have data belonging to N clients stored in a single column of a database table. Each ...
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How many collisions (identical pairs) are possible in meet in the middle attack on double DES with two unique keys?

I was reading my professors slides, I understand how meet in the middle works, but I have a few confusions. So we need two $\{(P_1, C_1), (P_2, C_2)\}$. Let $\lg{(k_1)} = \lg{(k_2)} = 56$, we generate ...
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Secure CCA Encryption under Partial Key Exposure

I'm currently learning about chosen ciphertext attack and stumbled across a problem on CCA security. If I have an encryption scheme $(Gen,Enc,Dec)$, which is CCA-secure with $Enc:\{0,1\}^n\times \{0,1\...
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Combining algorithms for password storage?

Is it more secure to combine algorithms for password hashing, for example, Scrypt, Bcrypt, SHA-3, etc.? If an attacker wants to use dedicated hardware, he would need one for each algorithm. However, I ...
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Encrypt files on harddrive with double encryption

So I've been stuck on this question for a very long time. How do you use double encryption to encrypt a hard disk so that all of the following conditions are met: All data on the hard disk is ...
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How to determine the maximum number of times the DES algorithm needs to be run?

I am only a beginner in cryptography and I am getting confused by the following: Question Consider a known-plaintext attack performed on a double-DES cryptosystem. (a) Determine the maximum number ...
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How do additional input output pairs help with a Meet in the Middle attack on Double DES

Double DES is vulnerable to a Meet in the Middle attack where an attacker generates intermediate values and then matches them up to find candidate key pairs. For Double DES using $56$ bit keys and $1$ ...
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XORing Algorithm Outputs To Guard Against Breakthroughs

My question is how safe is XORing two algorithm outputs together... ...For Symmetric Encryption: Master key from CSPRNG ==> MK HKDF-Expand(...
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Weakness in double encryption [duplicate]

In the "Introduction to Cryptography: With Coding Theory" by Trappe and Washington, in the chapter about DES algorithm the authors say that: "If double encryption is equivalent to single encryption,...
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Why is double encryption that's equivalent to single encryption no better than single encryption?

In the "Introduction to Cryptography: With Coding Theory" by Trappe and Washington, in the chapter about DES algorithm the authors say that: "if a cryptosystem is such that double encryption is ...
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The security level of double encryption

Let PKE $\Pi' = (Gen', Enc', Dec')$ and it is secure in the sense of $S'$. Let PKE $\Pi'' = (Gen'', Enc'', Dec'')$ and it is secure in the sense of $S''$. $S'$ and $S''$ may be separation which means ...
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Is an invulnerable code possible (including brute force attack)?

If I double encrypted a text with for example AES wouldn't it be invulnerable to bruteforce attacks due to the computer not knowing when it has reached the plain text? Plain text->1st layer of ...
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Best practices when encrypting a file with three different ciphers [closed]

I have some files that contain important information, so I want to encrypt them by the most secure encryption method possible. I've read countless StackExchange answers on similar questions and some ...
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Database vs SAN vs Network Encryption

Good day everyone! Please bear with me as this is my first post on the crypto exchange. An interesting question was raised in a meeting recently about the double-encryption problem (i.e. same ...
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double encryption - One Time Pad

Can the security of the encryption system be improved by using double encryption with two randomly chosen keys? By double encryption I mean using two keys K1 and K2, each 20-bit long, to obtain ...
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Multiple encryption using the same key

I am a newbie to this area. I have a program that uses a custom algorithm to encrypt a message. I can encrypt it as many times as I want, but using the same key. I have couple of questions so that I ...
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Trading Chosen-Ciphertext-Protection for Double encryption

Straight to the point: I'm trying to implement double encryption using two cipher suites. One (#1) of them is a stream cipher without any checksum/authentication guarantee, the other (#2) is an AEAD ...
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Reverse cascaded AES encryption

I was wondering if it is possible to decrypt a cipher-text using a single key which was encrypted twice. For example: Let's assume that we encrypt a plaintext using AES-CTR and encrypt the output ...
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How can Alice enable Bob to look-up values in a private map

I think this problem is similar to private set intersection, yet distinct in a way where: Alice has an extensive Mapping of say id to name id1 -> John Doe id2 -> Jane Doe id3 -> Edgar Poe ...
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Multiple Encryption - One-Time Pad

It is known that One-Time Pad(OTP)s are theoretically unbreakable but impractical for use because of the size of the key length. But what if multiple encryption is used? Not to encrypt the first ...
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Are some combinations of Substitution + Transposition more vulnerable than others?

Iterating multiple substitution ciphers is not mathematically different from using a single substitution cipher (3 Vigenere iterations with a 31-, a 32-, and a 33-letter key would essentially be a ...
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When does a multiple Vignere cipher become intractable?

Multiple Vignere ciphers do not repeat the key until the message gets longer than the LCM of the cipher lengths. Are messages shorter than that safe? If not, what is the attack strategy? I believe ...
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Does the double-hash H(H(x)) have greater collision probability than H(x)?

Let $H$ be a collision resistant hash function and $P_c[H](S)$ the collision probability about a sample set $S$ of input elements (eg. random numbers). It increases with double hash? That is, $P_c[H\...
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Using multiple cryptographic keys for encryption?

I am setting up an encryption methodology for items in a database. To decrease the likelihood of data being compromised due to the keys being compromised I would like to use an application level key (...
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Safely using ciphers that take small key sizes

Is it feasible to use triple encryption for block ciphers with the maximum keysize being the only significant security issue? I mean $C = E_{k_1}(E_{k_2}(E_{k_3}(P)))$ and $P = D_{k_1}(D_{k_2}(D_{k_3}(...
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What is the difference between a dual cipher and a tweak?

I have looked at the idea of dual ciphers but I cannot convince myself I really understand them. I think I just need a very simple worked example. I was given the definition: Two ciphers $E$ and $E′$...
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Multisignature or Multi-password File

I want to create a file that I could give to 3 trusted friends, and allow any two of them to decrypt it when together (or in sequence when not physically in the same place). This is similar to a ...
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Revocation of users in encrypted storage system?

How can you design an encrypted storage system, that allows adding and removing users without sharing a common secret and having to re-encrypt everything when a user is removed? My partial idea is: ...
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Finding Vigenere's keys with part of decrypted text?

I have a text that was encrypted twice with two Vigenere keys. However, I know the seven first characters of the decrypted text. I have already implemented a function displaying for the five first ...
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Signal Double Ratchet - How can Alice send 2+ messages in the beginning of the Signal Protocol?

I'm studying about Signal Protocol and I had a doubt in Double Ratchet Algorithm. This section describes how to derive the receiving and sending key messages. Alice is initialized by Bob public ...
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Double Ratchet Algorithm - What if the receiving wants to send the second message before the initiator?

I'm studying about Signal Protocol and I had a doubt in Double Ratchet Algorithm. This section describes how to derive the receiving and sending key messages. But in this scenario, only Alice can send ...
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“Double Encryption” using the same cipher?

When it comes to the words "double encryption", I cringe. What I see is the following scenario play out. Someone has plain text and they encrypt it with the AES cipher using the 14 round variant, so ...
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What 'exactly' are AES dual ciphers?

I recently posted a question about AES dual ciphers based on a certain understanding of them. Now I am not so sure if my understanding is correct. AES: a question about dual ciphers and security ...
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Is it worth using custom encoding on top of standard encryption?

I am using standard encryption AES/CBC. I wonder if I can invest some time adding my own custom encoding/decoding after the encryption just as an extra security layer. Does it really add any value ...
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Is there a system where multiple people can encrypt a message and then decrypt it in any order? [duplicate]

For example, A encrypts a message. B encrypts that. C encrypts that. Then B decrypts, followed by A then C. Are there systems that allow this? Does such a property have a name?
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Is this scheme multi-message secure? [closed]

Let $G$ be a pseudorandom generator. Is the scheme with encryption $$\text{Enc}_k(m) = s \| \left( m\oplus G(k) \oplus s \right),\quad s\in\{0,1\}^n \text{ uniformly sampled},$$ and decryption $$\...
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Multi party anonymous key distribution

Consider a protocol, wherein Alice wants to send a message $M$ to many friends $F_1, F_2, \dots F_n$, from whom she has (some form of) public keys ($e_{F_i}$, with private key $d_{F_i}$). She does not ...
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Multiple public key encryption

Sorry for the newby question but would this work: Alice encrypts a message X with John's public key to form Y. Alice then encrypts Y with Bob's public key to form Z. Alice then sends Z to Bob and John....
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possibility to encrypt data using AES and RSA frequently? [closed]

I am doing a research for encrypting data, I found many research doing multiple encryption using DES and RSA ? but in symmetric cryptography the best algorithm is AES so I need to do multiple ...
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Are Two Ciphers Better Than One? i.e. RC4 and AES

OK It's cringe time (or hopefully not) I know this is probably a variation of an old and dragged out question or so you may think but let me ask away and hopefully get some insight. Google a while ...
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Encrypting messages for multiple recipients

With hybrid cryptography, I want to encrypt a message intended for multiple recipients. This can be archived (as described here by creating a symmetric secret key, encrypt the message with this key, ...
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Can a MITM attack be applied to this construction?

On reading the accepted answer to this question, I was wondering whether a Meet In The Middle attack could be applied to the suggested construction (below), and if not, then what is the effective key ...
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Is there any way to have a coded string such that it can be decoded in multiple ways?

This is more out of curiosity than anything, having no knowledge of cryptography. But say I have strings "test1" and "test2", is there any way/algorithm to encode the two strings to an encoded string ...
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Why isn't the maximum security of triple DES 48 * 2 vs 56 * 2?

The security of quadruple or even more encryption isn't much more than that of double encryption. But each round also counts as one encryption. So why isn't triple DES only 96-bits secure?
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Require x of y possible passwords to decrypt

Is there a way to set up encryption so that a certian number (x) out of a total (y) number of users/passwords are required to do the decryption? Background: This is mostly a thought experiment, and ...
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Repeated NONCE in CTR mode

My understanding is that, in CTR mode, the NONCE must be unique because, if a NONCE is reused, multiple plaintexts will be XORed with the same value and this gives an attacker leverage to decrypt the ...