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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 ...
Lery's user avatar
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26 votes
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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 ...
Lery's user avatar
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13 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 ...
Gilles 'SO- stop being evil''s user avatar
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 ...
untra's user avatar
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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, ...
Squeamish Ossifrage's user avatar
11 votes
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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 ...
Squeamish Ossifrage's user avatar
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 ...
fgrieu's user avatar
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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 ...
Yehuda Lindell's user avatar
7 votes
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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 ...
kodlu's user avatar
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6 votes
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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 ...
fgrieu's user avatar
  • 140k
6 votes
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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, ...
Aleph's user avatar
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6 votes
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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 ...
fgrieu's user avatar
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5 votes
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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, ...
Chris's user avatar
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5 votes
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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 ...
poncho's user avatar
  • 146k
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 ...
DannyNiu's user avatar
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5 votes
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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 ...
Maarten Bodewes's user avatar
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4 votes
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Questions about future and session key generation in DUKPT process

I don't know where you're seeing session keys. DUKPT is designed to do transactions, not sessions, hence the name. If some application is using them for sessions that is probably a bad idea. (added ...
dave_thompson_085's user avatar
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 ...
Maarten Bodewes's user avatar
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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 ...
mikeazo's user avatar
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4 votes
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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 ...
Gilles 'SO- stop being evil''s user avatar
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 ...
Ilmari Karonen's user avatar
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 ...
Ilmari Karonen's user avatar
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,...
forest's user avatar
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4 votes
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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: ...
Gilles 'SO- stop being evil''s user avatar
3 votes
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How 3DES work in a simple way?

3DES encryption chains 3 DES operations with 3 different DES keys $K_1$, $K_2$, $K_3$ (each 8-octet with 1 bit ignored per octet) together forming the key of 3DES (24-octet with 168-bit key), to ...
fgrieu's user avatar
  • 140k
3 votes

Question on 3DES keys

For high security applications using 3DES, NIST recommends using keying option 1 (all keys are different). This is simply because it's the safest. For any application, keying option 1 should be used. ...
Daffy's user avatar
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3 votes
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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 ...
otus's user avatar
  • 32.1k
3 votes

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

DES: the key length is short enough to brute force it. One known plaintext-ciphertext is enough to get the key(s). There is at least one website which offers to crack one of these for $30 in a few ...
Nova's user avatar
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3 votes
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How can two keys have the same KCV?

You're using 2-key 3DES, right? DES and 3DES has the property that the least significant bits of the key don't actually contribute to the encryption process; hence any two keys that differ only in ...
poncho's user avatar
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