2
votes
2answers
95 views

Linear cryptanalysis complete key guessing

In linear crypt analysis, partial sub keys are guessed and verified for its correctness with the help of plaintext and ciphertext. From the partial sub key, how it is possible to guess the complete ...
12
votes
2answers
836 views

Is it possible to utilize an AES-128 encryption hardware unit for AES-256?

There exist processors (for example ARM v8/v9 archicteture based), which cannot do AES-256 hardware based, but are equipped with AES-128 encryption hardware units. Is it possible to utilize an AES-...
1
vote
1answer
26 views

Determining the degree of freedom for a chi-squared test on a strict avalanche criterion matrix

I have read that the degree of freedom is calculated by subtracting 1 from the number of states a random variable can be in. I am performing a goodness of fit test on a 64*32 strict avalanche ...
2
votes
1answer
720 views

How does certificate-based encryption solve key revocation problem?

How does certificate-based encryption solve key revocation problem? For example, if a user accidentally reveals its secret key or an attacker compromises it, the user may request revocation of its ...
3
votes
2answers
3k views

How does a client verify a server certificate?

As far as I know, when I request a certificate from Verisign (for example), and after they approved that me is me, they create a certificate (for me) which contains the digital signature and public ...
7
votes
1answer
219 views

How to generate a key using any $m$ passwords out of total $n$?

My application requires an AES-256 key K for some secure operation. In order to avoid saving this key in application, I have implemented following scheme: There ...
1
vote
0answers
22 views

Should we use exponent 3 in RSA-OAEP?

As I understand it the proof that RSA-OAEP is secure in the random oracle model is much tighter for exponent 3. Does that mean that exponent 3 should be chosen?
0
votes
1answer
56 views

File using same key on XOR cipher. Using CBC [closed]

I have some files that are encrypted using an unknown key and it's using the CBC method to encrypt the files. When I XOR two files together the first two bytes are always the same, but different for ...
0
votes
0answers
27 views

Concatenated Key Question - Poly-alphabetic Substitution and Columnar Transposition

I am working on a degree module, and have been tasked with designing an Encryption/Decryption algorithm. I hope to receive some help with a couple of questions, if possible. Apologies if terminology ...
0
votes
1answer
76 views

Clifford Cocks Interview: “Raising numbers to a power with the product as modulus”

Disclaimer: I'm new to cryptography Background: Clifford Cocks, the former GCHQ mathemetician and crytologist, gave an interview where he said: "My thinking was that you need something that is ...
4
votes
1answer
58 views

VIC cipher author known?

Does anybody know if the design of VIC cipher is attributed to anybody? I've tried Google and found nothing. There are quite a few sites describing the method in detail, a few implementing it ...
6
votes
1answer
303 views

One cipher to rule them all?

I learned from Dan Boneh's course that many cryptographic primitives (prngs, stream ciphers, hashes, hmac, key derivation functions) can be built from just one a block cipher or PRF. For example, the ...
1
vote
0answers
39 views

How to encrypt an image with logistic chaotic map?

I need to encrypt color images, using logistic chaotic map. Could you please recommend an algorithm for this? All the articles that I've found on the Internet are completely unclear.
1
vote
0answers
15 views

Why does HS1-SIV allow forgeries when the SIV collides, even when the PMN does not collide?

The HS1-SIV authors claim that forgeries are possible if an SIV collision occurs. However, I do not understand how this is possible unless the PMN collides too. Otherwise, the collision will be in ...
1
vote
0answers
42 views

Is parallel, vectorized NORX nearly as fast as hardware-accelerated AES-GCM?

As I understand it, NORX gets 3.5 CPB in an unoptimized implementation. But NORX can be parallelized. With 4-way SIMD, I would expect about 7/8 CPB performance. This is nearly as good as AES-GCM in ...
12
votes
2answers
4k views

Is TrueCrypt's multiple/cascading encryption safe?

Is TrueCrypt use of cascading encryption safe? Is it useful? TrueCrypt is arguably one of the most popular and widely used encryption applications in use today, yet it seems to use a very ...
0
votes
0answers
39 views

Is pseudo-random letter insertion secure?

Is pseudo-random letter insertion a secure mechanism? I mean by expanding the key or taking two parameters in the encryption function, you select positions in the text at which to insert random ...
1
vote
0answers
40 views

AES - Size of T-Boxes and obtaining T-Box values

In article "A high performance ST-Box based unified AES encryption/decryption architecture on FPGA" (http://www.sciencedirect.com/science/article/pii/S0141933115001945) two 32Kb dual-port BRAMs are ...
4
votes
1answer
51 views

Is there any IND-CPA secure stream cipher with a “standard” hardness assumption?

I've read our recent question: "One-time pad using RSA and Diffie-Hellman functions" which asks about the security of a particular way to convert RSA and discrete exponentiation into a stream cipher. ...
1
vote
1answer
65 views

UKS attacks. Dangers & Prevention?

I am trying to understand how to prevent a UKS (unknown key-share) attack, but I am having trouble finding many resources out there to help. Let's imagine a hypothetical secure messaging application ...
0
votes
0answers
30 views

generate unpredictable value with a shared key

Is there any function that taek a key to generate (un)predictable value ? I hope you will more understand more what I mean with this example f take in input an array, a key and a round number f(...
0
votes
1answer
86 views

One-time pad using RSA and Diffie-Hellman functions

Suppose that Alice and Bob use an encryption algorithm based on a one-way function $F$ (Eve knows it), and $r$, a secret key shared between Alice and Bob (Eve doesn't know it). Key is computed as: $K =...
0
votes
0answers
31 views

Key size limitations due to software compatibility?

At the moment, much popular encryption-based software routinely handles up to 4096 bit keys and standard usage is broadly migrating from 1024 to 2048 bit keys. Hashes widely used are MD5/SHA1/SHA256 (...
1
vote
1answer
182 views

How many bits of symmetric security does RSA-3072 actually provide? [duplicate]

I know that the sizes are standardized to $1024$, $2048$ etc. but they actually provide different security than $128$, $256$... for example $\texttt{RSA-}2048$ is actually $112$ bits of security and $...
0
votes
1answer
98 views

Combining multiple PRGs together

Got some theoretical questions about PRGs to solve (given by lecturer for self-learning, no score involved). Tried to find on the internet but couldn't figure out how to solve them, so I will mention ...
0
votes
1answer
55 views

can anyone explain inversion per byte?

I am designing the truncating block of SHA3 algorithm , there its given that first we need to do the inversion per byte of the 1600 bit output and then truncating it to give 512 bits output. Can any ...
1
vote
1answer
87 views

Is it safe to use the same IV for multiple encryptions in AES CBC mode when you are always encrypting random bytes?

I am generating random bytes (16 or 32 bytes at a time), and I want to encrypt them using a 128 bit AES key in CBC mode. Am I really weakening this horribly if I am reusing the same IV and key each ...
1
vote
1answer
84 views

How can public key not reverse encryption if the algorithm is known? [duplicate]

I've been reading about WhatsApp getting "end-to-end" encryption, and when reading about it, I've notice something. If I want to send a message from cell $A$ to cell $B$, since there's a public key, ...
3
votes
0answers
45 views

Can you give me a summary of cryptographic hardness assumptions?

Until recently, I had a link to a website which summarizes up-to-date cryptographic hardness assumptions. But, unfortunately I cannot find it. The webpage is categorized well problems such as, DL ...
5
votes
2answers
99 views

What asymmetric key exchange algorithms are known besides DH?

On Wikipedia, a lot of the subjects that are said to be different key exchange methods are often just protocols that incorporate the Diffie-Hellman algorithm into them. The only other key exchange ...
29
votes
4answers
115k views

How secure is AES-256?

The cipher AES-256 is used among other places in SSL/TLS across the Internet. It's considered among the top ciphers. In theory it's not crackable since the combinations of keys are massive. Although ...
2
votes
1answer
73 views

Trusted Third Party Cryptanalysis Labs?

There's no doubt that third party cryptanalysis is an essential part of the crypto ecosystem. It's how we know that there's some degree of practical "goodness" to a new algorithm or protocol. Unlike ...
1
vote
2answers
116 views

Homomorphic Encryption with Addition and Exponentiation

Is there any homomorphic encryption scheme which supports addition and power over cipher text ? Paillier is close but it supports addition and multiplication with a constant. I am getting an output ...
1
vote
1answer
276 views

Do I need to use a MAC with asymmetric encryption?

The internet has drilled into me that when I delivery any symmetrically encrypted data, I should also deliver a MAC to authenticate it before any decryption occurs. Do I also need to do this if I use ...
1
vote
1answer
43 views

Monoalphabetic cipher using different languages in the same plaintext

Today I learned the principle of the monoalphabetic cipher. It's simple to decrypt a ciphertext written all in the same language (english for example) because I can use the syntactic properties as ...
0
votes
0answers
24 views

Filling in MD5 input variables

I have a majority of an input string(as well as the total length) and the output for an MD5 hash. Is there a way to calculate the remaining input bytes that I am missing?
2
votes
0answers
52 views

CryptDB data re-encryption and onion layers

From the CryptDB paper , I understoond that the onion layers once decrypted are not re-encrypted. Only columns which are queried infrequently will be re-encrypted to higher onion layers. But if we ...
3
votes
1answer
5k views

Is it safe to use PBEWithMD5AndDES?

I'm encrypting some of my (not so much important) files with PBEWithMD5AndDES. Is it a strong method or it can be de-crypt easily without knowing my selected ...
2
votes
0answers
44 views

Unpredictable value rotation

I have very vey basic skills in cryptography, it's hard for me to explain clearly my problem so I will start with an example. Estimote beacons have a security function called secure UUID, once ...
1
vote
1answer
64 views

What are the possible security issues when exporting a plaintext database to a file like this?

Say I have plaintext database with key-value pairs of usernames and passwords. Then I iterate through the database, encrypt the passwords, and write the username and encrypted password pairs to file ...
2
votes
1answer
170 views

Is $H'(M) = 5M + 9H(M) \pmod{2^n}$ a secure hash function?

theorem: For arbitrary $i≥0$ there exists $m,n≥0$ such that $35+i=5m+9n$. We can use this theorem for constructing simple hash function. Let $M$ be message and $H(M)$ be its hashed value with hash ...
2
votes
1answer
379 views

About the Security of PCBC Encryption Mode

We are designing an encrypted file system. We plan to use the PCBC (Plaintext Cipher Block Chaining) encryption mode for encryption. This is because we desire the feature ("small changes in the ...
4
votes
2answers
1k views

Is there something wrong with my decryption using key=9, mod 26?

I am new to cryptography and have started looking at some basic encryption. I have the following question to answer: Decrypt the the following encrypted quotation using ...
4
votes
1answer
330 views

For RSA keys, is the safety of a given key-length different for signing vs encryption?

I'm wondering if considerations of key-length are different when thinking about signing vs encryption. If for some reason, it was safter to use smaller keys for signing that would be interesting.
5
votes
1answer
138 views

How can I figure out a hash algorithm?

This may be trivial, and may be impossible... this is outside my field but willing to learn. I have a hardware device that accepts a network MAC address (6 bytes of data) like this: 38-60-77-EC-1D-33 ...
0
votes
1answer
54 views

Is webkey a reasonably secure authentication system?

I just created Webkey in the last couple days. This should allow any website to do single-password auth with a much higher level of auth security and convenience for users (single password with ...
0
votes
0answers
16 views

Can XTS + checksum be used for authenticated encryption?

Is it possible to use XTS+a checksum for authenticated encryption? Specifically, it seems like a good $n$ bit checksum applied before encryption should ensure that any change to the ciphertext ...
0
votes
0answers
22 views

Is it okay to use Threefish-512 in ECB mode with Poly1305 MAC to protect some AES keys?

A person has some independent AES-GCM-SIV keys they need to protect as part of a hypothetical protocol or product, where it is publically known that it is in fact AES-GCM-SIV keys that are being ...
0
votes
1answer
39 views

Product of Vigenère ciphers is not a Vigenère cipher with length of LCM

I have always thought that using two Vigenère ciphers leads to another Vigenère cipher with key length of LCM (least common multiple) of the two previous Vigenère ciphers. But I have stumbled upon ...

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