57
votes
Is Triple DES still considered safe to use?
Well, yes and no.
Triple DES using 3 different keys is still considered secure because there are no known attack which completely break its security to a point where it is feasible nowadays to crack ...
- 7,479
26
votes
Accepted
Why would anyone choose 3DES over AES in software?
In my opinion, there are no reason to choose 3DES over AES, ever.
Especially if it is in software, since 3DES performances have always been terrible. Furthermore, most CPUs ship with AES accelerators ...
- 7,479
12
votes
Key sizes supported by 3DES
The triple DES (3DES) block cipher works by essentially running the block through DES three times. Triple DES is also known as "DES EDE" (encrypt-decrypt-encrypt) and under the name given by the ...
- 140k
12
votes
Is Triple DES still considered safe to use?
NIST just recently (11/27/2017) put out a bulletin that Triple-DES will be deprecated in the future, and will be disallowed in protocols like TLS and IPsec, with a future deprecation timeline to be ...
- 121
12
votes
Cryptographic methods that do not use prime numbers?
There is none. All cryptography involves the number 2, which is prime, whenever dealing with information in strings of bits—or in esoteric cases like ROT13, well, there's a prime number right there, ...
- 47.2k
11
votes
Accepted
Can I find the encryption key if I know the plain text and the encrypted text (DES and AES)?
The most cost-effective way to do this is to try each key and see if it works. The expected number of trials is $2^{55}$ with DES, $2^{127}$ with AES-128, and $2^{255}$ with AES-256.
You can speed ...
- 47.2k
11
votes
What is DES-EDE3-CBC?
At least in the context of PKCS#5 (which is commonly seen through the encryption of PEM files), DES-EDE3-CBC is Triple DES with three keys, used in CBC mode, with unspecified padding.
Yes, “EDE” means ...
9
votes
Calculating 3DES Key Check Value (KCV)
Three problems here:
The online tool used expects a 24-byte (48 hex-character) key; thus you should enter E6F1081FEA4C402CC192B65DE367EC3EE6F1081FEA4C402C as the ...
- 134k
7
votes
Meet-in-the-Middle attack on 3DES
The meet-in-the-middle attack on ciphers like $C=E^2_K(P)=E_{K1}(E_{K2}(P))$ works as follows.
Let's assume you're given a known-plaintext pair $(P_1,C_1)$ and a known-plaintext pair $(P_2,C_2)$
You ...
- 45.5k
7
votes
Is a 4DES or 5DES system possible?
There is a very interesting paper that relates to this exact question (but you wouldn't guess it from the title). The paper is titled Efficient Dissection of Composite Problems, with Applications to ...
- 27.4k
7
votes
Accepted
How can I attack a Triple-Block cipher with 2 keys (like 3DES) with a cost of ≤ 2⁵⁶
As far as I know your attack is the best attack known, unless something better has very recently been published.
Please note that for DES as the basic cipher the chosen $A$ may not work, but you can ...
- 19.9k
6
votes
Accepted
Special case of 3DES
EEE with $K_1$=$K_2$=$K_3$ is measurably less insecure than EDE with $K_1$=$K_2$=$K_3$, because the former has 48 rounds, but the later reduces to just one encryption E, thus 16 rounds. Two ...
- 134k
6
votes
Accepted
Is it possible to perform a meet-in-the-middle within a block cipher?
Meet-in-the-middle attacks can indeed be used for block cipher (but also hash function) cryptanalysis. As mentioned in the question, this goes back to Diffie and Hellman's analysis of DES. However, ...
- 1,816
6
votes
Accepted
3DES security when K1=K3
TL;DR: the official $2^{80}$-something theoretical security of 2-Key Triple DES w.r.t. key search¹ is still practically good enough in most of its many uses in 2020; but security authorities rightly ...
- 134k
5
votes
Accepted
Do 2DES and 3DES2 have the same effective key length?
Definitely a mistake. The text clearly contradicts itself.
... 2DES has an effective key length of 57.
And later...
There does not
appear to be a meet-in-the-middle attack on 3DES2 however, ...
- 243
5
votes
Accepted
Why do 1st and 3rd key have to be the same in 2 key 3DES?
In two key 3DES two keys are equal so that key size is only 112 bits, compared to the 168 bits of full 3DES. The advantage is a smaller key size without a correspondingly large loss in security: both ...
- 31.8k
5
votes
Accepted
How DES/AES can guarantee by feeding different secret keys, the encrypted outputs are different?
I am learning the meet-in-the-middle on DES attack.
I don't know of any meet-in-the-middle attack on DES; I'll assume you're talking about 2DES (where you apply DES with one key $k_1$, and then apply ...
- 140k
5
votes
Why didn't people redesign the key scheduling algorithm of DES to use longer keys instead of using 3-DES?
Same as the reason of why not switching to AES (or any other 80+ key bits algorithms available at the time).
Because we want to reuse whatever "hardware" (chip design) resources available to do the ...
- 8,263
5
votes
Accepted
Security Strength of Symmetric vs Asymmetric Ciphers
It means that you should be able to retrieve a key using $2^{112}$ operations, assuming a normal attack scenario and the most efficient method of attack at this time, assuming that the rest of the ...
- 90.2k
4
votes
Accepted
What is the complexity for attacking 3DES in linear or differential cryptanalysis?
"Not vulnerable" is not how I would describe it, but my understanding is that the existing attacks on DES cannot directly not work with 3DES.
At the moment, the best attack against single DES is a ...
- 3,517
4
votes
Modes of Triple DES - When to use each?
Triple DES has been standardized by NIST as DES-EDE. So the EEE versions are usually not present in cryptographic libraries. Using them is not advisable for this reasoning alone. Hardware will not ...
- 90.2k
4
votes
Can I find the encryption key if I know the plain text and the encrypted text (DES and AES)?
In the case of DES and AES, it turns out that having a plaintext/ciphertext pair does not really make finding the key any more feasible than just having a ciphertext.
As you are hopefully already ...
- 38.3k
4
votes
Accepted
Does C# Triple DES Encryption need 128 bit key or 192 bit key
The documentation states
This algorithm supports key lengths from 128 bits to 192 bits in increments of 64 bits.
Which is a somewhat strange, but comprehensible, way of stating that you can pass ...
4
votes
What is the keyspace of 2-key 3DES?
Yes, two-key triple DES has a 112-bit keyspace. That is to say, it has 2112 distinct possible keys, each of them made up of two arbitrarily chosen 56-bit single DES keys.*
Note that, for historical ...
- 45.7k
4
votes
Is there any encryption algorithm that, with small change in input will produce big change in the encrypted output?
What you want, if at all possible, is an IND-CPA (or, preferably, even IND-CCA2) secure encryption scheme. Such encryption schemes are by definition probabilistic (and/or stateful), so that even ...
- 45.7k
4
votes
How fragile is 3DES nowadays?
There are three main issues with 3DES that an application needs to be aware of:
Small block size – 3DES has a small 64-bit block size. When encrypting non-negligible amounts of data with a single key,...
- 14.9k
4
votes
Accepted
Why are credits cards using 3DES instead of AES?
The main reason is history. Credit cards with chips have been around for longer than AES. However, it is not true that 3DES is strictly less secure than AES.
DES has two weaknesses compared with AES: ...
3
votes
Why do 1st and 3rd key have to be the same in 2 key 3DES?
If we want to make three successive DES encryptions or decryption using 2 secret keys K1, K2 at least one time, and possibly a ...
- 134k
3
votes
Accepted
Why does 3DES need private key to decrypt?
Yes, 3DES is a symmetric cipher and you use a secret key for both encryption and decryption with it. However, that is not the same thing as the keys used in RSA or other public key cryptography – you ...
- 31.8k
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