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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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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 ...
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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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1answer
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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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1answer
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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 ...
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The protocol of provisioning shared key to multiple devices?

I have a bunch of IoT devices which can do ECDH/ECDSA and AES. They all are connected to some server and know its public key. In turn, server knows each public key of the corresponding device. Devices ...
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Order of multiple encryption algorithms

as you can see on image above, in VeraCrypt you can select either Serpent -> Twofish -> AES or ...
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Majority encryption algorithm?

Assume that I want to leave an encrypted message to a group of $n$ people in a way that they can only decrypt it if they work together in the following sense: For some fixed $k < n$ every sub-...
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How would multiple uses of a vigenère cipher be decrypted on paper (classic)?

As far as I can tell (from reading the Wikipedia article about it) decrypting a message encrypted with the vigenère cipher is possible on paper. But what would happen if the message is encrypted ...
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Can double-encrypting be easier to break then either algorithm on its own?

As was pointed out in Martin Bonner's comment I cannot prove this, but it seems intuitively impossible. An encryption function is supposed to obscure the plaintext to the point where no information ...
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Is a 4DES or 5DES system possible?

We know that 3DES is created with $E_{K_3}(D_{K_2}(E_{K_1}(m)))$ to extend DES's key length. Is it possible to extend it further by repeating this pattern? Perhaps using $E_{K_5}(D_{K_4}(E_{K_3}(D_{...
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Affine Cipher over an Affine cipher

I would like to know your view about the title, encrypting a plain text with an affine cipher then encrypting that ciphertext once more using the same cipher, but of course different keys. Would it be ...
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References for cascade [closed]

I have found many sources against cascading encryption, however I am having trouble finding arguments FOR using cascading. AES-256 + BlowFish + RC5 etc... each with a different key. This is for ...
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Is super encryption (aka “multiple encryption”) always good?

I'm trying to use super encryption (also known as “multiple encryption”) with AES in CFB mode with IV and password salting and AES in CTR mode both without padding. I first use AES CFB and then AES in ...
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Combining a block cipher with a (pseudo) OTP

One of the drawbacks of OTP is that it can require an inconveniently long key. Besides that, it doesn’t provide data authentication. Therefore, I have been working on an algorithm idea, which I hope ...
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Can Grover's Algorithm be combined with a meet-in-the-middle attack?

We all know and love the meet-in-the-middle attack which basically makes double encryption pointless using a time-memory-tradeoff. Now there was recently the recommendation by the NSA to use double ...
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357 views

Adding dummy bytes to ciphertext

I was wondering if interleaving the resulting crypted data with dummy bytes placed at random positions but known in advance by the peers could improve security (no matter the algorithm and strength ...
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How strong can multiple encryption be?

Suppose I encrypted a homophonic substitution cipher at the level of syllables, trigrams, digraphs, and individual letter with a Vigenere cipher using the keyword cryptography. I would then encrypt ...
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Combining several symmetric ciphers using XOR

I have seen a talk by Rüdiger Weis, where he says that you can combine two symmetric ciphers using XOR. According to him, that has the effect that its sufficient if only one of the ciphers is secure. ...
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Attack on Double Encryption Scheme

In this protocol: A → B : { <[A, {K}pk(B)]> }pk(B) B → A : { <[B, {K}pk(A)]> }pk(A) I'd like to determine why this is insecure. How can the attacker learn the key K if A and B are both honest ...
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Proving existence of an encryption scheme that has indistinghuishable multiple encryptions in the presence of an eavesdropper, but is not CPA-secure [duplicate]

I got stuck in trying to find a solution to the 3.7 exercise of the Katz-Lindell book. The exercise also assumes the existence of a pseudorandom function. The problem is that a multiple messages ...
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Combining cascaded encryption keys into one key

Is there an encryption algorithm where it's possible to combine multiple encryption keys into one, so that: $E_{AB}(Data) = E_A(E_B(Data))$ KeyAB should be computable from KeyA and KeyB, but it must ...
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Misunderstanding Broadcast Encryption [duplicate]

I have a secret message which I want to encrypt such that any of several different keys can open it independently. The keys can't know about each other and it has to be able to work completely ...
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Multiple encryption of part of block

Is there any security risk in encrypting parts of blocks twice? I'd like to get around block sizes and make encrypted messages just as long as the unencrypted ones: Block 1: Byte 0 - 7 Block 2: Byte ...