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Questions tagged [3des]

A block cypher encryption algorithm built from applying three iterations of the original DES algorithm.

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38
votes
1answer
16k views

Why do we use encrypt-decrypt-encrypt (EDE) in 3DES, rather than encrypting three times?

I'm wondering why we use encrypt-decrypt-encrypt (EDE) sequence in 3DES (also known as DES-EDE, TDES or TDEA) with three keys instead of three times encryption (EEE) with three different keys?
35
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2answers
21k views

Is Triple DES still considered safe to use?

What it says on the tin. Is it still used in things like TLS?
18
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1answer
18k views

Why is triple-DES using three different keys vulnerable to a meet-in-the-middle-attack?

Among other sources, this wikipedia entry states that triple DES using three seperate keys (k1, k2, k3) is vulnerable to meet-in-the-middle-attacks, while triple DES using only two keys (k1, k2, k1) ...
17
votes
1answer
4k views

Why would anyone choose 3DES over AES in software?

I'm well aware of what NIST and PCI say about the usage of 3DES and its deprecation/disallowance and I also know that AES is the actual recommended standard for software and hardware encryptions. I'm ...
9
votes
1answer
914 views

Why should CAST5 and 3DES not be used for encrypting files over 4GB?

On https://www.gnupg.org/faq/gnupg-faq.html#define_cast, it says that Like 3DES, its 64-bit block size means it should not be used to encrypt files larger than 4Gb in size… How and why does the ...
9
votes
1answer
1k views

How can I attack a Triple-Block cipher with 2 keys (like 3DES) with a cost of ≤ 2⁵⁶

I am trying to solve something and I have but I have no idea anymore. Maybe anyone of you has an idea/solution/hint. Given is a block cipher $F$ with key length $n$. It looks like this: $$c = ENC_{k1}...
8
votes
1answer
366 views

Is there a security proof for the Triple-DES construction in the ideal cipher model?

Suppose one has an ideal block cipher $E \: : \: \{0,\hspace{-0.04 in}1\hspace{-0.03 in}\}^k \times \{0,\hspace{-0.04 in}1\hspace{-0.03 in}\}^w \: \to \: \{0,\hspace{-0.04 in}1\hspace{-0.03 in}\}^w \;...
7
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2answers
2k views

What does it mean if second half of 8-char string encrypted in 3DES is always identical?

In the recent Adobe passwords leak, presumably encrypted in 3DES ECB, second half of all 8-character passwords is identical: ioxG6CatHBw== Source: http://pastebin.com/iDTFARwq (guesses based on ...
7
votes
1answer
10k views

What is U2FsdGVkX1?

Using CryptoJS 3.1 I noticed that using 3Des, the encrypted message always start with U2FsdGVkX1 Why is the first part of the encryption always the same? What information does this hold and how ...
5
votes
1answer
881 views

Is TripleDES 168bit vulnerable to Differential Cryptanalysis?

I was reading this paper. In the table-1 of the paper it says TripleDES (showing both 128bit and 168bit keysize) is vulnerable to Differential Cryptanalysis. It also says that AES (showing all three ...
5
votes
1answer
164 views

Has a Two Key TDES encryption ever been successfully attacked?

Is there any known instance of a Two Key TDES ever being successfully attacked (in real life), when the key is used to encrypt less than $2^{20}$ words?
5
votes
1answer
737 views

Brute Force on 3DES with Reduced Keyspace and Unknown IV

I'm trying to brute force a 3DES problem given a reduced keyspace (ie I know the first half of the key) but with an unknown IV. The code decrypts to plaintext. My first thought was that I could set ...
5
votes
2answers
189 views

Is it possible to perform a meet-in-the-middle within a block cipher?

Standard meet-in-the-middle explanations show that you can perform a meet-in-the-middle attack on a repeated block cipher such as double-DES (performing DES twice in a row). However, block ciphers ...
4
votes
1answer
252 views

Does anyone have a KAT for 3DES KO-2?

Does any one have, or can refer to a Known-Answer-Test (KAT) for Triple DES Keying Option 2? (Keying Option 2 means $C = DES_{k_1}(DES^{-1}_{k_2}(DES_{k_1}(P)))$ for encryption and $P = DES^{-1}_{k_1}...
4
votes
2answers
1k views

What is the keyspace of 2-key 3DES?

I am assuming that 2-key 3DES is equivalent to 2DES. I know the key size is 2x56 = 112 bits. Is this key size the same as the keyspace? e.g. Would the keyspace be 112 bits ($2^{112}$)?
4
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0answers
667 views

Key expiration policy for 3DES / TDES / Triple DES

I have a system that signs plain text messages using a message authentication code (MAC) encrypted with 3-key Triple DES. The short message is used on connection to establish a session key, so it ...
4
votes
1answer
2k views

Effective key length of Two-Key Triple-DES

What's the effective key length of Two-Key Triple-DES, for some (possibly several) reasonably well-defined and sensible definitions of effective key length, say assuming attack using ample chosen ...
3
votes
1answer
20k 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 ...
3
votes
2answers
367 views

Composition of block ciphers and 3DES

There is some intriguing things about DES and 3DES. Now, I know that DES is weak and 3DES was an attempt to construct a more secure block-cipher from a deprecated one. Having this in mind, what ...
3
votes
1answer
250 views

Special case of 3DES

3DES uses EDE as it is backward compatible to single DES, but consider the following case $K_1$=$K_2$=$K_3$ which one is more secure EDE or EEE.
3
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2answers
2k views

Modes of Triple DES - When to use each?

I'm studying for CISSP certification & am using Shon Harris Exam Guide. It states that there are 4 modes that Triple-DES can be used in: DES-EEE3 DES-EDE3 DES-EEE2 DES-EDE2 I understand these ...
3
votes
2answers
585 views

How to calculate leaked information from a check digit

Given a check digit calculated using mod 11, of an encrypted numeric sequence of 8 digits, how much information can be known about the plaintext? More specifically, a single 3DES encrypted CBC block ...
3
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2answers
242 views

Have these compositions of block ciphers the same security?

I'm interested by the compositions of the block cipher DES, instantiated with independent keys $k_1$, $k_2$ and $k_3$. Are these 3 compositions equivalent in terms of security? $$DES_{k_1}(DES_{k_2}(...
3
votes
2answers
4k views

How can 3DES encryption use decryption in the middle step?

I have been reading about the 3DES algorithm and I cannot understand one part. In 3DES we do following operation: $$C=E[K_3,D[K_2,E[K_1,P]]].$$ Where $C$ is ciphertext, $P$ is plaintext, $E$ is DES ...
3
votes
3answers
268 views

Does 3-DES take approximately the same time to encrypt 1B and 1KB?

I am using 3-DES to encrypt some data in Java. I decided to run some tests and plot some graphics to decide how to optimally pack data for its encryption (see how encryption/decryption time behave ...
3
votes
1answer
97 views

Sweet32: Can a single 8 byte block session ID be exploited by this vulnerability?

Im currently developing a authentication scheme. The authentication scheme will use a 64 bit encryption to encrypt its session ID. Here is how the authentication system will work: For each session, ...
3
votes
1answer
2k views

Generating an IV for ESP 3DES-CBC

I have an application written in C, running in Linux. It uses IPsec (ESP) (manually putting the IPSec packet together) to send certain packets. The algorithm used ...
2
votes
3answers
594 views

Can ECB mode really leak some characters?

In an Ars Technica article about Adobe's use of 3DES in ECB mode, there's a paragraph The passwords, according to password expert Steve "Sc00bz" Thomas, are encrypted in a mode known as ECB. That ...
2
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2answers
484 views

Why do 1st and 3rd key have to be the same in 2 key 3DES?

From this answer: However, that wasn't the only situation they had in mind; they also considered the case where someone implemented 2 key 3DES in hardware (which the first and last subkeys were ...
2
votes
4answers
11k views

Can I find the encryption key if I know the plain text and the encrypted text (DES and AES)?

If I have the plain text and its output after encryption with a key K1, is it algorithmically feasible to find K1? I am specifically interested in the cases of DES and AES encryption algorithms.
2
votes
3answers
19k views

Calculating 3DES Key Check Value (KCV)

I am trying to verify a Triple DES Key Component generated by PC Crypto. The key portion is: E6F1081FEA4C402CC192B65DE367EC3E and the KCV value that should be ...
2
votes
1answer
2k views

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_{...
2
votes
1answer
6k views

Why is Triple DES not vulnerable to meet in the middle attacks?

Consider the Triple DES encryption calculated as: $$C= E_{K_1}(D_{K_2}(E_{K_1}(P))).$$ For a chosen plaintext attack, given plaintext $P$, we compute the result of $D_{K_2}(E_{K_1}(P))$ and store ...
2
votes
2answers
1k views

Do 2DES and 3DES2 have the same effective key length?

I am following the notes "Introduction to Modern Cryptography" by Bellare and Rogaway, and on the chapter about blockciphers there is the following claim (page 11 of https://cseweb.ucsd.edu/~mihir/...
2
votes
2answers
13k views

Meet-in-the-Middle attack on 3DES [duplicate]

How can I apply the Meet-in-the-Middle attack to the 3DES algorithm, and why does the literature say that 3DES is more secure than DES?
2
votes
1answer
494 views

Can the key-complement property of DES be used against 3DES?

The comments in this recent question about the security of 3DES made me wonder if the key complement property of DES (which reduces its security by ~1 bit) can be used in the meet-in-the-middle attack ...
2
votes
2answers
511 views

3DES over Galois Counter Mode (GCM) for authenticated encryption

Is it possible to use DES or 3DES over Galois Counter Mode (GCM) to provide authenticated encryption? I haven't seen any implementation yet.
2
votes
1answer
526 views

OpenSSL des-ede3 not producing same output as test vector implies it should be

I'm encrypting one of the standard TDEA/3DES/DES-EDE test vectors with openssl: ...
2
votes
3answers
7k views

ANSI X9.31 standards for generating random numbers

The NIST-Recommended Random Number Generator Based on ANSI X9.31 Appendix A.2.4 Using the 3-Key Triple DES and AES Algorithms has 3DES being used three times for each 64-bit block of random data ...
2
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1answer
191 views

Would XDES be more secure than 3DES, where X is a number > 3?

Would XDES be more secure than 3DES, where X is a number > 3? Like 10DES... If so why aren't we using it?
2
votes
1answer
798 views

Why does 3DES need private key to decrypt?

I create two files, my.cer and my.pem ( include certificate and private key), I encrypt a file with my.cer, I use openssl smime -encrypt command. When decrypting data, it needs my.pem. I think 3DES ...
2
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1answer
249 views

Question on 3DES keys

The official NIST publication I saw says for federal applications 3DES with three keys should be used. I have such questions: what does it mean federal? Does it mean for industrial applications that ...
2
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2answers
2k views

Triple-DES DUKPT CBC PIN variant vs Data variant

Does any know the difference between triple des dukpt decryption algorithm with PIN variant and Data variant? I have done Triple DES DUKPT PIN variant, which generate session key from KSN and BDK. ...
2
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1answer
1k views

What is the complexity for attacking 3DES in linear or differential cryptanalysis?

I know that 3DES is NOT vulnerable to DC , LC . But is it because the attacks requires too many input\output pairs ? Or because it's impossible ? (i.e requires more than 2^64 pair )
2
votes
1answer
2k views

Find out which keying option is being used in Triple DES?

As far as I know, there are three standard options for the three keys $K_1$, $K_2$ and $K_3$ used by 3DES: Three distinct keys. The first and last key are equal: $K_1$ = $K_3$. Three equal keys: $K_1 ...
2
votes
1answer
830 views

test vectors for 3DES seem to in fact be testing DES - not 3DES

NIST SP 800-20 Appendix A has what presumably are supposed to be test vectors for 3DES except almost all of the test vectors utilize 8-byte keys and not the 24-byte keys that 3DES is supposed to have. ...
2
votes
1answer
578 views

Using MITM to attack three keys 3-DES encryption?

I know that MITM can break three keys into two parts $(K_1,K_2)$ and $K_3$ where the worst time complexity is $2^{112}$. My questions is whether we are able to break three keys $(K_1,K_2,K_3)$ into ...
2
votes
0answers
28 views

Do I need verifiable shares?

I'm using Shamir's secret sharing in a 2:3 system. Thus a secret Key is split in 3 subkeys (KeyS:KeyC:KeyT) I've 3 entities at ...
2
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0answers
54 views

Extracting RC4 and 3DES keys from system memory

I have read papers [1], [2] that have presented techniques on extracting symmetric encryption keys from memory during the process of encryption. There are tools [3] that can extract AES keys from ...
2
votes
0answers
202 views

HBCI Encryption/Decryption

I need help during implementation of C# interface (.NET framework) for encryption of messages which are sent to/from HBCI (Homebanking Computer Interface) server according to RDH-10 standard. ...