instruction stringlengths 15 30k |
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[RFC4493] describes the generation of AES-CMAC and padding for messages with length > sizeof(aes128_key). However I need to generate the CMAC for a series of messages shorter than 16 byte.
So I'd like to ask if it is viable to:
- Pad M0 with 0 up to 16 bytes
- Pad M_last with the proposed padding (first bit 1,... |
I'm wondering, if something like block cipher with big block size is a good memory-hard function?
All memory-hard key derivation functions I've seen look more complex than that, which made me question my understanding of memory-hardness.
The following function looks memory-hard (memory tradeoff looks expensive) t... |
I'm working on a security project. I need to perform a sorting on the lists of encrypted integers and strings. The encryption used in symmetric. The clients send the encrypted data in a list to the server (encrypted by different symmetric keys, each key is shared b/w a client and the server). On receiving the list, ser... |
First the obvious; checking $M_L=D_L$:
- is unnecessary from a security standpoint ***IF*** $H$ really is secure, by definition of that; but who knows what's really secure?
- can't harm preimage resistance (first or/and second), nor collision resistance;
- can greatly increase speed, if the hash is computed only a... |
Can you encrypt an image (with AES) such that you can open it as a png/jpeg? |
If you encrypt an image (AES), is it still an image and can you view it? |
You actually can. You actually can do even more: encrypt a file format into an other. You need to play with key and IV to get that the message input is "well" transformed by the encryption. If you control the key and the IV and the initial and final file you ave enough freedom to achieve your aim.
Ange Albertini made ... |
You actually can. You actually can do even more: encrypt a file format into an other. You need to play with key and IV to get that the message input is "well" transformed by the encryption. If you control the key and the IV and the initial and final file you ave enough freedom to achieve your aim.
Ange Albertini made ... |
If you aim to show the effect of the encryption, meaning a scrabled image you have to encrypt only the "image data" and keep the file structure unchaned. A simple tutorial can be found here: https://blog.filippo.io/the-ecb-penguin/.
Author uses ppm files, but you can easily adapt to your file format.
# First ... |
I don't have the background for dealing with Riemann hypothesis but is well known that covers the prime distribution below a specified number.
In order to solve the RSA problem you have to factor the semiprime or calculate the totient itself, that's hard as factoring the modulus.
Question is, could Riemann hypothesis... |
Could Riemann hypothesis solve certainly RSA? |
I'm working on a security project. I need to perform a sorting on the lists of encrypted integers and strings. The encryption used is symmetric. The clients send the encrypted data in a list to the server (encrypted by different symmetric keys, each key is shared b/w a client and the server). On receiving the list, ser... |
I'm working on a security project. I need to perform a sorting on the lists of encrypted integers and strings. The encryption used is symmetric. The clients send the encrypted data in a list to the server (encrypted by different symmetric keys, each key is shared b/w a client and the server). On receiving the list, ser... |
While bruteforcing a ciphertext, I've found multiple keys which produce the same result.
Mode is DES with ECB and PKCS5 padding.
ciphertext is `TXcmk8KwIPxTHR45zAIGJPEFYj6dsgVOGseZnMcedCOhl/Qp5a8Qig==`
keys are used: `{ !*}`, `{ +}`, `{ *}`
The tried keys are delimited by brackets `{}` and ... |
Does DES support different keys that lead to the same result? |
Trying to settle a discussion at work. We are mostly concerned with pre-image resistance.
Suppose we have a common secure hash function $H$ (e.g. SHA-1/SHA-2) and some message $M$ we want to hash. The message has length $M_L$. For the message we provide the digest $D$ and the length of data digested $D_L$.
With r... |
Consider the following protocol for two parties to flip a fair coin.
Trusted party T publishes her public key pk
A chooses a random bit bA, encrypts it under pk, and announces the ciphertext cA to B and T
B does the same and announces a ciphertext cB
T decrypts cA and cB, and announces the results... |
Consider the following protocol for two parties to flip a fair coin.
Trusted party T publishes her public key pk
A chooses a random bit bA, encrypts it under pk, and announces the ciphertext cA to B and T
B does the same and announces a ciphertext cB
T decrypts cA and cB, and announces the results... |
Gen generates Pk and Sk (l bits each), Enc encrypts m (length l) but by bit using each bit of Pk respectively, Dec decrypts ciphertext bit by bit using each bit of Sk respectively. How do I prove this scheme is not IND-CCA-2 secure? |
How do I prove that a bit by bit PKE scheme (that is IND-CPA secure) for an n-bit message is not IND-CCA-2 secure? |
I came upon an idea the other day that I had some questions about. I am not a security professional but I do study with an amateur interest and have not heard of this particular idea before.
There were a few similar questions here, but :
- http://crypto.stackexchange.com/questions/10140/using-one-way-hash-fu... |
I keep seeing the term "Cryptographic Agility" referenced. What does it mean?
For instance:
https://msdn.microsoft.com/en-us/library/windows/desktop/bb204775(v=vs.85).aspx
> One of the key value propositions of CNG is cryptographic agility, sometimes called cryptographic agnosticism.
http://research.micro... |
What is cryptographic agility? |
Consider the following protocol for two parties to flip a fair coin:
* Trusted party $T$ publishes her public key $p_k$
* A chooses a random bit $b_A$, encrypts it under $p_k$, and announces the ciphertext $c_A$ to $B$ and $T$
* $B$ does the same and announces a ciphertext $c_B$
* $T$ decrypts $c_A$ and $c_B$, an... |
I have one sender, and a small number (~5) of recipients. The sender knows each recipient's public EC key. I want the sender to broadcast a single message in such a way that any one of the recipients can decrypt it. For reasons that aren't completely technical, I'd like the security properties of the encryption algorit... |
A standard extension of ECIES for multiple recipients (broadcast / multiparty)? |
> When I do ECIES, can I omit the MAC $d$? An attacker doesn't gain
> anything by tampering with the session key, since that just causes the
> inner decryption or MAC check to fail.
I wouldn't rely on that property. Please don't do this.
> Can I use the same ephemeral EC pair $R=rG$ for all recipients?
Yes, ... |
Consider following authentication protocol.
Client *ClientA* knows some initial secret KeyA shared with server.
Client also knows IP of legitimate server.
Now when client wants to establish connection with server she will send KeyA to server and her ID (for server to know which key to use).
The server generat... |
Cryptographic agility is the capacity for an IT system to easily evolve and adopt alternatives to the cryptographic primitives it was originally designed to use.
An example (and building block) for cryptographic agility is the X.509 certificate format, which is defined with various signature algorithms, hash algorit... |
Some AES [implementations][1] in crypto libraries make use *only 8-bit byte operations on the cipher state*, like in the [lorawan-parser][2] (cf [lib/aes.h][3]).
When I try to understand the implications of that, I wonder if normal cipher states in "standards" implementation uses more bits or not ? In the [AES wikip... |
What are the security implications of an AES implementation that uses only 8-bit byte operations on the cipher state? |
Cryptographic agility is the capacity for an IT system to easily evolve and adopt alternatives to the cryptographic primitives it was originally designed to use.
An example (and building block) for cryptographic agility is the X.509 certificate format, which is defined with various signature algorithms, hash algorit... |
Cryptographic agility is the capacity for an IT system to easily evolve and adopt alternatives to the cryptographic primitives it was originally designed to use.
An example (and building block) for cryptographic agility is the X.509 certificate format, which is defined with various signature algorithms, hash algorit... |
Cryptographic agility is the capacity for an IT system to easily evolve and adopt alternatives to the cryptographic primitives it was originally designed to use.
An example (and building block) for cryptographic agility is the X.509 certificate format, which is defined with various signature algorithms, hash algorit... |
Cryptographic agility is the capacity for an IT system to easily evolve and adopt alternatives to the cryptographic primitives it was originally designed to use.
An example (and building block) for cryptographic agility is the X.509 certificate format, which is defined with various signature algorithms, hash algorit... |
Consider following authentication protocol.
Client *ClientA* knows some initial secret KeyA shared with server.
Client also knows IP of legitimate server.
Now when client wants to establish connection with server she will send KeyA to server and her ID (for server to know which key to use).
The server generat... |
I want to inquire that what are requirements of the audio input to be encrypted using AES. Is encrypting a mp3 file different from encrypting an aac file?
Thanks! |
What are requirements of the audio input to be encrypted using AES? |
There are a few issues with your protocol. Namely it doesn't protect against men-in-the-middle.
Issue #1 (mentioned by fgrieu in the comments): Assume I host one of the (many) servers all your IP packets have to travel through from ClientA to Server. If I drop the server's Key1A (or KeynA) any future request won't w... |
There are a few issues with your protocol. Namely it doesn't protect against men-in-the-middle.
**Issue #1** (mentioned by fgrieu in the comments): Assume I host one of the (many) servers all your IP packets have to travel through from ClientA to Server. If I drop the server's Key1A (or KeynA) any future request won... |
There are a few issues with your protocol. Namely it doesn't protect against men-in-the-middle.
**Issue #1** ([mentioned by fgrieu in the comments][1]): Assume I host one of the (many) servers all your IP packets have to travel through from ClientA to Server. If I drop the server's Key1A (or KeynA) any future reques... |
[MonkeyDuplex][1] constructions defined by Keccak authors has padding in every duplex block.
Why only last duplex block is padded in [NORX][2]?
Is it because NORX has domain separation, or simply because Keccak authors defined duplex on top of sponge and it isn't actually needed, or ...?
[1]: http://keccak... |
I came upon an idea the other day that I had some questions about. I am not a security professional but I do study with an amateur interest and have not heard of this particular idea before.
There were a few similar questions here, but :
- http://crypto.stackexchange.com/questions/10140/using-one-way-hash-fu... |
I have one sender, and a small number (~5) of recipients. The sender knows each recipient's public EC key. I want the sender to broadcast a single message in such a way that any one of the recipients can decrypt it. For reasons that aren't completely technical, I'd like the security properties of the encryption algorit... |
MonkeyDuplex in NORX does not have padding per duplex because it does not need thanks to domain separation. As the plaintext is mixed into the ciphertext, it does so at the sponge rate, the same way as Keccak does during normal sponge operations. This makes it more efficient at the given security level.
The standard... |
Is there short period in AES 128 key schedule? |
I am comparing the actual probability of no collisions to the probability approximation formula of no collisions from the Understanding Cryptography text.
The approximation is as follows:
P(no collisions) = e^-(t(t-1))/2*2^n
I know that t represents the number of elements but I am confused about the d... |
Cryptographic agility is the capacity for an IT system to easily evolve and adopt alternatives to the cryptographic primitives it was originally designed to use.
An example (and building block) for cryptographic agility is the X.509 certificate format, which is defined with various signature algorithms, hash algorit... |
I am comparing the actual probability of no collisions to the probability approximation formula of no collisions from the Understanding Cryptography text.
The approximation is as follows:
$$P(\text{no collisions}) = \frac{e^{-t(t-1)}}{2 \cdot 2^n}$$
I know that t represents the number of elements but I am c... |
I have confused about the effect of different Block sizes on AES performance. as you can see [here][1] , there is a huge gap between the throughput of different block sizes. as far as i know, every 16 bytes must be encrypted separately but i don't know what would happened when the block sizes would be increased?
how ... |
How differnet Block sizes Can efffect on the throughput of GPU implementation of AES? |
I'm trying to add the authentication for my One-Time Pad implementation.<br>
I know that to provide Unconditionally Secure Authentication I need to use the [One-Time MAC authentication][1].
But I don't understand why a solution as the following (that's a lot more easy to implement) doesn't provide the same security... |
Remember, a GPU consists of a large number of computational engines, all controlled by the same instruction stream. That is, there might be 64k processors, and all those processors can work on different pieces of data, but they must all do the same thing to all of them. We refer to this as [SIMD][1] parallelism.
W... |
I'm learning the multiplication operation on EC. From most material I can found, the multiplication $nP$ is just:
$$nP=P+P+\cdots +P+P$$
For negative factor, i.e. $(-n)P$, by above definition and the definition of $-P$, we can write $(-n)P$ as:
$$(-n)P = (-P) + (-P) + \cdots (-P)$$
My question is: is it possi... |
I'm learning the multiplication operation on EC. From most material I can found, the multiplication $nP$ is just:
$$nP=P+P+\cdots +P+P$$
For negative factor, i.e. $(-n)P$, by above definition and the definition of $-P$, we can write $(-n)P$ as:
$$(-n)P = (-P) + (-P) + \cdots (-P)$$
My question is: is it possi... |
I'm trying to add the authentication for my One-Time Pad implementation.<br>
I know that to provide Unconditionally Secure Authentication I need to use the [One-Time MAC authentication][1].
But I don't understand why a solution as the following (that's a lot more easy to implement) doesn't provide the same security... |
I'm trying to add the authentication for my One-Time Pad implementation.<br>
I know that to provide Unconditionally Secure Authentication I need to use the [One-Time MAC authentication][1].
But I don't understand why a solution as the following (that's a lot more easy to implement) doesn't provide the same security... |
I am confused about the effect of different block sizes on AES performance. As you can see [here][1], there is a huge gap between the throughput of different block sizes. As far as I know, every 16 bytes must be encrypted separately, but I don't know what would happen if the block sizes would be increased.
How woul... |
How do different block sizes affect the throughput of GPU implementations of AES? |
Quoting an old question:
[1]: http://crypto.stackexchange.com/questions/1199/random-coin-flip-using-elgamal-and-a-trusted-party
Consider the following protocol for two parties A and B to flip a fair coin (more complicated versions of this might be used for Internet gambling):
1. A trusted party T publishes her p... |
[Quoting an old question:][1]
> Consider the following protocol for two parties A and B to flip a fair
> coin (more complicated versions of this might be used for Internet
> gambling):
>
> 1. A trusted party **T** publishes her public key *pk*.
> 2. **A** chooses a random bit $b_A$, encrypts it using *pk* a... |
I'm trying to add the authentication for my One-Time Pad implementation.<br>
I know that to provide Unconditionally Secure Authentication I need to use the [One-Time MAC authentication][1].
But I don't understand why a solution as the following (that's a lot more easy to implement) doesn't provide the same security... |
Consider the following the following RSA public key pk = (N, e) = (1457, 1307).
(a) Knowing that 187^2 = 1 mod 1457 find the factorization of N.
(b) Given the factorization of N computed above, use the CRT to decrypt the following ciphertext
c = Epk(m) = 3.
For part a) I am not sure which property of modular arit... |
Consider the following the following RSA public key $pk = (N, e) = (1457, 1307)$.
(a) Knowing that $187^2 \equiv 1 \pmod {1457}$ find the factorization of $N$.
(b) Given the factorization of $N$ computed above, use the CRT to decrypt the following ciphertext
$c = E_{pk}(m) = 3$.
For part a) I am not sure whic... |
I am trying to understand why Merkle Tree doesn't suffer the birthday attack?
Can you help me?
Thank you! |
Why Merkle Tree doesn't suffer Birthday attack? |
How all necessary parameters are shared between signer and verifier in ED25519 signature scheme? |
What is the current state of research on quibit commitment?
It seems that the answer is not [2001][1] but it seems to me that a lot of these pdf are referring to a old protocols of quantum bit commitment [1997][2], where the impossibility of that scheme has been proved for a unconditionally (or perfect) security of ... |
What is the current state of research on quibit commitment?
It seems that the answer is not [2001][1] but it seems to me that a lot of these pdf are referring to a old protocols of quantum bit commitment [1997][2], where the impossibility of that scheme has been proved for a unconditionally (or perfect) security of ... |
Imagine I have client and server running on different machines, each as a separate software.
I want to ensure:
1. message authenticity, integrity and confidentiality
2. and also I want to be able to detect if someone copied my client software and is trying to make requests from a different machine
Now to solve ... |
Is my protocol that uses hybrid cryptography and AES-GCM secure? |
Imagine I have client and server running on different machines, each as a separate software.
I want to ensure:
1. message authenticity, integrity and confidentiality
2. and also I want to be able to detect if someone copied my client software and is trying to make requests from a different machine
Now to solve ... |
Imagine I have client and server running on different machines, each as a separate software.
I want to ensure:
1. message authenticity, integrity and confidentiality
2. and also I want to be able to detect if someone copied my client software on different machine and is trying to make requests there
Now to solv... |
Imagine I have client and server running on different machines, each as a separate software.
I want to ensure:
1. message authenticity, integrity and confidentiality
2. and also I want to be able to detect if someone copied my client software on different machine and is trying to make requests there
Now to solv... |
Imagine I have client and server running on different machines, each as a separate software.
I want to ensure:
1. message authenticity, integrity and confidentiality at least of messages coming from client.
2. and also I want to be able to detect if someone copied my client software on different machine and is t... |
How is the One Time Pad (OTP) perfectly secure? |
Optimal same-base exponentiation? |
Imagine I have client and server running on different machines, each as a separate software.
I want to ensure:
1. message authenticity, integrity and confidentiality at least of messages coming from client.
2. and also I want to be able to detect if someone copied my client software on different machine and is t... |
I am new to cryptography and have a question about a use of Vigenere encryption in the case of small strings. I'd like to encrypt keywords, smaller than 10 characters.
If I use Vigenere separately for each keyword I can have a key longer than 10 characters, and making each string impossible to break (if I use a diff... |
Consider the NP language SAT.
A Non-Interactive proof for SAT is the following:
- The Prover given an instance of SAT (namely, a boolean formula on n-variable) return to the Verifier a valid assignment.
- The verifier given an instance and a proof applies the assignment defined by the proof on the instance and... |
I am new to cryptography and have a question about a use of Vigenere cipher in the case of small strings. I'd like to encrypt keywords that are smaller than 10 characters.
If I use Vigenere separately for each keyword I can have a key longer than 10 characters, and making each string impossible to break (if I use a ... |
You stated:
> **"I can at the very least narrow down the list of possibilities."**
Here's an example of why OTP is perfect secrecy, and why your statement, although true, doesn't matter.
I have a sentence which I wrote, and after encrypting it with an OTP, it looks like this:
> aaaaaaaaaaaaaaaaaaaaaaaaaaaaa... |
Considering a home pc/laptop as machine used (Say typical 2.4 GHz, 16GB RAM, 4 core processor) for running GNFS algorithm. What would be the largest number that could be factored into its prime factors in milli seconds ? rather how many digits such number might have ? |
Can anyone tell me if an encryption / decryption scheme like the following exists?
`Encrypted1 = SomeCryptoFunction(Data, Key1)`
`Encrypted2 = SomeAdditionalCryptoFunction(Encrypted1, Key2)`
`Data = SomeDecryptFunction(Encrypted1, Key1)`
`Data = SomeDecryptFunction(Encrypted2, Key2)`
In words, the idea i... |
Considering a home pc/laptop as machine used (Say typical 2.4 GHz, 16GB RAM, 4 core processor) for running any factorization algorithm. What would be the largest number that could be factored into its prime factors in milli seconds ? rather how many digits such number might have ? |
my doubt is about the existance of a dynamic RSA accumulator with deletion of an element in O(1) time.
Do you know some practical implementation? |
Can anyone tell me if an encryption / decryption scheme like the following exists?
`Encrypted1 = SomeCryptoFunction(Data, Key1)`
`Encrypted2 = SomeAdditionalCryptoFunction(Encrypted1, Key2)`
`Data = SomeDecryptFunction(Encrypted1, Key1)`
`Data = SomeDecryptFunction(Encrypted2, Key2)`
In words, the idea i... |
My question is about the existence of a dynamic RSA accumulator with deletion of an element in O(1) time.
Do you know some practical implementation? |
I am studying RSA Dynamic Accumulator and I have a question: why is simpler to calculate the new accumulator value after a deletion if is known the secret ϕ(n)? Is possible to calculate the deletion only with the RSA modulus N? |
I am trying to understand what are the benefits of using [Damgård–Jurik][1] over Paillier. I understand that expansion factor decreases as `s` increases. But isn't it the case that this comes at the expense of security? If your goal is to reduce space overhead compared to Paillier then you might choose a smaller securi... |
I wish to send some small data that RSA alone can encrypt, and I send a shared secret along with it.
A --> B ; RSA(data,shared_secret)
vs
A --> B ; RSA(data,shared_secret) + SHA-256(data,shared_secret)
Will verifying the shared secret be enough for message integrity and authenticity? Or, should I also send ... |
I wish to send some small data that RSA alone can encrypt, and I send a shared secret along with it.
A --> B ; RSA(data,shared_secret) // B will verify the shared_secred and authenticate A;
vs
A --> B ; RSA(data,shared_secret) + SHA-256(data,shared_secret)
Will verifying the shared secret be enough for mes... |
How do I find the differential characteristics using techniques Shrinking ?
How do I extract the key on Differential Cryptanalysis using the technique Shrinking in Blockcipher Algorithm?
Shrinking technique is a technique that was made by Eli Biham for cryptanalysis Skipjack 1998. |
If I design a lightweight algorithm,
How do I calculate gate equivalents (GE) in lightweight algorithm?
and what are the parameters of the algorithm was called "Lightweight"?? |
While I haven't heard of previous work on this exact problem,
splicing together some standard solutions to a few other problems almost solves this problem.
There is a loophole in the [pigeonhole principle][1]:
if the output file is bigger than the input image,
it is possible to store "extra" information.
Start... |
I'm working on a code that needs to perform modular multiplication of big numbers several times. Since the operation takes place several times, using division to find the remainder is very expensive. Repeated subtraction with the mod value also takes a lot of time because big numbers are involved.
So is there any ot... |
what is the fastest and efficient method to perform modular multiplication? |
I'm working on a code that needs to perform modular multiplication of big numbers several times. Since the operation takes place several times, using division to find the remainder is very expensive. Repeated subtraction with the mod value also takes a lot of time because big numbers are involved.
The following comm... |
I have to derive master key from n-secret key. With the help of master key, i can collect all the secret keys which is used to derive master key.
key1, key2,..keyN ==> **single master key**
and
**single master key** ==> key1, key2,..keyN
is this even possible??
|
If we have a random key $K$ which is 256-bit, and have a block cipher $C$ which has a block size of 128-bit. Is it safe to encrypt $K$ with $C$ in ECB mode?
This problem can be generalized to given a block cipher $C_0$ which has a block size of $k$-bit and a random bit string $S$ whose length is $n \cdot k$ where $n... |
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