instruction stringlengths 15 30k |
|---|
I had a go at writing a PHP script to do the brute force attempt. Using a common list of passwords dictionary file it found the password in 8 seconds.
$target = 16978476480;
function utf8_to_unicode($str) {
$unicode = array();
$values = array();
$lookingFor = 1;
... |
I am aware of at least RSA, El Gamal, and variations of ECC all relying on different problems and that those problems are considered hard.
However, if someone figures out a way to break this security, it's hard to imagine the consequences. Or what if some intelligent service published certain elliptic curves, whe... |
Why are we not using multiple ciphers per message? |
I don't know about computing things in parallel, so I will ignore that part of the question.
First, please note that the encryption algorithm is rarely the the weak point of the security. It is far more likely that
- you will have problems with the implementation,
- some spyware installed on your computer,
- a... |
I am trying to crack an unpadded RSA set up for a homework.
I have public key (R,e) and encrypted message E.
R:=1189873858375600120035497781492406260116261348762168101523668479976252918878873543993974091515716923413521166189;
e:=7;
E:=9356889972925702305775485384173712916868921873425258331884305687... |
How can I make up private key(private exponent) with P,Q,DP1,DQ1,PQ? |
I have a basic question related to Identity and Attribute based encryption.
Construction of IBE scheme was first shown by Boneh et al. in 2001 and I think in 2004 Sahai and Waters introduced Attribute based encryption in 2004 for multiple attributes. ABE extended to CPABE or KPABE schemes.
Can ABE schemes be con... |
I don't know about computing things in parallel, so I will ignore that part of the question.
First, please note that the encryption algorithm is rarely the the weak point of the security. It is far more likely that
- you will have problems with the implementation,
- some spyware installed on your computer,
- a... |
Is **SRP-6a** post-quantum secure? If it is not post-quantum secure, do any post-quantum secure alternatives similar to **SRP-6a** exist? |
I am aware of at least [tag:rsa] RSA, [tag:elgamal-encryption], and variations of [tag:elliptic-curves] relying on different problems and that those problems are considered hard.
However, if someone figures out a way to break this security, it's hard to imagine the consequences. Or what if some intelligent service ... |
I am aware of at least [tag:rsa], [tag:elgamal-encryption], and variations of [tag:elliptic-curves] relying on different problems and that those problems are considered hard.
However, if someone figures out a way to break this security, it's hard to imagine the consequences. Or what if some intelligent service publ... |
I want to know about these tags in RSA Encryption by private Key. when I use this code:
using (var provider = new RSACryptoServiceProvider(keySize))
{
publicKey = provider.ToXmlString(false);
privateKey = provider.ToXmlString(true);
}
It create this xml:
<RS... |
I want to know about these tags in RSA Encryption by private Key. when I use this code:
using (var provider = new RSACryptoServiceProvider(keySize))
{
publicKey = provider.ToXmlString(false);
privateKey = provider.ToXmlString(true);
}
It create this xml:
<RS... |
I translate the Shamir secret sharing as bellow:
we add the secret to degree $d$ polynomial whose coefficients are chosen uniformly at random from for instance Z_p and this polynomial does not have any constant term.
Now my question is : would it be secure to multiply the secret by the aforementioned polynomial an... |
What is h refer to in this RSA variant? |
I am little curious about how do we calculate hardness proof of any cryptography algorithm?
Also where can I find hardness proof for AES and AES-CBC ?
|
Hardness proof? |
>I am little curious about how do we calculate hardness proof of any cryptography algorithm?
This is typically done by assuming some problem is hard (e.g., solving discrete log). Then proving that if someone can break the cryptography algorithm (e.g., diffie-hellman) that they can also break the hard problem. Once t... |
Suppose implement the Shamir secret sharing as following: we select a degree $d$ polynomial $P$ with a zero coefficient of 0, and all other coefficents selected randomly from $Z_p$; and to this polynomial $P$, we add the secret as a constant term $Q = P + secret$. If we use $Q$ as the polynomial in our Secret Sharing ... |
For security in Shamir secret sharing we need that the coefficients of the polynomial are independent and uniformly random in the field. Multiplying the polynomial by a constant from the field does not change this, so yes, you can do it and still be secure.
In fact, in multiparty computation, something akin to this ... |
Reading about triple DES and understanding the principles, I am still curious how Firefox defines their three keys for the encryption/decryption.
Suppose that the user saves his passwords in the browser without a master key, are the default keys randomized and saved to the separate file?
Also, if the user enters a ma... |
I assume you are asking how the password a user enters to unlock their saved user data is translated into the keys used by 3DES? I did some Googling but the information doesn't appear to be readily available. I can say that, in general, 3DES actually only uses two keys. There are different configurations, but I beli... |
In connection to a commitment scheme, how are witness and commitment different? Are 'Binding' and 'Hiding' properties defined w.r.t. witness and commitment or both? |
What is h in this RSA variant? |
I have researched the Blowfish algorithm and am curious as to why there exists no effective cryptanalysis for this algorithm as of yet. What basic principles or features allow [Blowfish][1] to achieve this?
[1]: http://en.wikipedia.org/wiki/Blowfish_%28cipher%29 |
How does Blowfish avoid successful cryptanalysis? |
This question came up as I tried to answer an earlier question I asked: http://crypto.stackexchange.com/questions/19244/cryptographic-data-structure-wanted-sparse-array-without-membership-test. I still have not resolved that question to my satisfaction, but this question may be appreciated independently.
I want an ... |
I assume you are asking how the password a user enters to unlock their saved user data is translated into the keys used by 3DES? According to [this link][1] DES-EDE-CBC, which is only two-key 3DES. The first and third keys are set equal to each other, resulting in two keys of 56 bits or a total size of 112 bits.
... |
> Is it significantly easier to reverse a sha256 hash if you know that the input was a 32 byte output of sha256?
Assuming a random N-bit input ($N>3256$) versus a 256-bit input, for all practical intents and purposes, the difficultly is extremely difficult (read: not feasible by today's computational capabilities) f... |
I am looking for a strong alternative elliptic curve cryptography, nothing created by the NSA and that could face quantum computing attack.
I heard about isogeny key exchange ie. supersingular isogeny, is it really secure? If you have an example that could be great.
What are the best alternative at the moment?
... |
I am looking for a strong alternative elliptic curve cryptography, nothing created by the NSA and that could face quantum computing attacks.
I heard about isogeny key exchange, i.e. supersingular isogeny, is it really secure? If you have an example that could be great.
What are the best alternative at the moment... |
I am looking for a strong alternative elliptic curve cryptography, nothing created by the NSA and that could face quantum computing attacks.
I heard about isogeny key exchange, i.e. supersingular isogeny, is it really secure? If you have an example that could be great.
What are the best alternatives at the momen... |
A side channel attack described [here][1]
I did not quite get , how the power measurements are used to get the
decryption key , can any body explain it?
[1]: http://hackaday.io/project/956/log/10108-aes256-is-not-enough-breaking-a-bootloader |
How did the power measurements translate to AES Key? |
Why are there a lot of duplicate file finder applications which are using MD5 Algorithm? What is the strength of MD5 in terms of searching duplicate files in hard disk or flash driver or any other storage device? |
A side channel attack is described [here][1].
I did not quite get , how the power measurements are used to get the
decryption key , can any body explain it?
[1]: http://hackaday.io/project/956/log/10108-aes256-is-not-enough-breaking-a-bootloader |
As a little pet project I'm writing some code to do a little cryptanalysis. Starting with something simple I have created a [hill climbing algorithm](http://en.wikipedia.org/wiki/Hill_climbing) for solving a simple substitution cipher.
So I start by generating a parent key by shuffling letters A-Z randomly. For the ... |
What is the translation for "hash" in french? |
As a little pet project I'm writing some code to do a little cryptanalysis. Starting with something simple I have created a [hill climbing algorithm](http://en.wikipedia.org/wiki/Hill_climbing) for solving a simple substitution cipher.
So I start by generating a parent key by shuffling letters A-Z randomly. For the ... |
As a little pet project I'm writing some code to do a little cryptanalysis. Starting with something simple I have created a [hill climbing algorithm](http://en.wikipedia.org/wiki/Hill_climbing) for solving a simple substitution cipher.
So I start by generating a parent key by shuffling letters A-Z randomly. For the ... |
The standard security property demanded of a blockcipher is that it be a pseudo-random permutation; i.e., given a uniformly random key, the blockcipher should be computationally indistinguishable from a random permutation under a chosen-plaintext or chosen-ciphertext attack.
However, what if the key is randomly sele... |
Has there been any cryptanalysis of AES under a non-uniformly distributed key? |
I am given the q, p, and e values for an RSA key, along with an encrypted message.
Here are those values:
`p = 1090660992520643446103273789680343
q = 1162435056374824133712043309728653
e = 65537
key = 299604539773691895576847697095098784338054746292313044353582078965`
I tried calculating d with the Extend... |
RSA given q, p and e? |
I am given the q, p, and e values for an RSA key, along with an encrypted message.
Here are those values:
p = 1090660992520643446103273789680343
q = 1162435056374824133712043309728653
e = 65537
key = 299604539773691895576847697095098784338054746292313044353582078965
I tried calculating d with the ... |
I am given the q, p, and e values for an RSA key, along with an encrypted message.
Here are those values:
p = 1090660992520643446103273789680343
q = 1162435056374824133712043309728653
e = 65537
sample ciphertext = 299604539773691895576847697095098784338054746292313044353582078965
I tried calculati... |
The standard security property demanded of a blockcipher is that it be a pseudo-random permutation; i.e., given a uniformly random key, the blockcipher should be computationally indistinguishable from a random permutation under a chosen-plaintext or chosen-ciphertext attack.
However, what if the key is randomly sele... |
Let $\Pi=(Gen_1,H_1)$ and $\Pi=(Gen_2,H_2)$ be two hash functions. Define $(Gen, H)$ so that $Gen$ runs $Gen_1$ and $Gen_2$ obtaining $s_1$ and $s_2$ respectively. Then let $H^{s_1,s_2}(x)=H^{s_1}(x)\|H^{s_2}(x)$, is it second pre-image resistant if at least one of $H^{s_1}$ and $H^{s_2}$ is second pre-image resistant?... |
I am looking for a strong alternative to elliptic curve cryptography. It should be something that could face quantum computing attacks, but nothing created by the NSA.
I heard about isogeny key exchange, i.e. supersingular isogeny, is it really secure? Otherwise, what would be an alternative that fulfills the above... |
I am looking for a strong alternative to elliptic curve cryptography. It should be something that could face quantum computing attacks, but nothing created by the NSA.
I heard about isogeny key exchange, i.e. supersingular isogeny, is it really secure? Otherwise, what would be an alternative that fulfills the above... |
What is the conceptual difference between the definition of *correctness* and *completeness* in verifiable cryptographic protocols? They justify that if a statement is correct then the verification should always successfully verifies. Is their any difference in the definitions? Or the one can substitute correctly the o... |
I've been searching for some time and have found no way to create a working certificate and private key pair with a DH or ECDH public key using OpenSSL. Once I do this, I'd like to sign it with an RSA key, too. Does OpenSSL support this? If so, how can I do it? |
I would like a data structure supporting two operations: $\mathsf{set}(k,v)$ and $\mathsf{get}(k)$, with the following properties:
1. $k$ can be any number between $0$ and something impressively large, like $2^{256}-1$.
2. If there is some $v$ such that $\mathsf{set}(k,v)$ has been called then $\mathsf{get}(k)$ ret... |
There seem to be many OID's that have been put in the ASN.1 tree that have the following ISO identified organization: OIW.
One example is SHA-1 (ElGamal seems to be another):
id-SHA1 OBJECT IDENTIFIER ::=
{iso(1) identified-organization(3) oiw(14) secsig(3)
algorithms(2) 26 }
Can a... |
We have $E(a)$, $E(b)$ encrypted under the same Paillier key.
As we all know, we can get $E(a+b)$ by calculating $E(a)*E(b)$.
But can we get $E(a-b)$, by calculating $E(a)/E(b)$?
I tried to calculate $E(a)/E(b)$ by using the *mpz_divexact* function in the [GMP](https://gmplib.org) library. But I cannot get the... |
How to do minus on plaintext in Paillier cryptosystem? |
How can I do minus on plaintexts in the Paillier cryptosystem? |
The NIST recommended elliptic curve domain parameters have the object identifiers named **secp** (i.e. **secp224k1**) and **sect** (i.e. **sect571k1**). What mean and what is the difference between **secp** and **sect** ? |
The NIST recommended elliptic curve domain parameters have names such as **secp**... (e.g. **secp224k1**) and **sect**... (e.g. **sect571k1**). What is the difference between **secp** and **sect**? |
> 1. As you can make up from this encryption scheme, I'm using the encrypt-then-authenticate approach to enforce ciphertext integrity. In step 2 of the decryption process I perform this authentication step. If the calculated HMAC turns out to be equal to the HMAC in the file, does this mean, apart from the implied ciph... |
**What benifits do substituion boxes and permutation boxes offer in DES?**
I understand that with more encryption rounds the more complex the ciphertext becomes due to multiple substitutions and permutations. What I don't understand is the purpose of these features.
I am under the impression that key length and ... |
I've looked up RC4 algorithm and it's seems easy enough but some parts of it seem random to me.
In the key schedule part take for example the following part :
j = (j + S[i] + key[i % keylen]) % 256
I can understand most of it, the key[i % keylen] is padding in-case that the key is shorter than 256 bytes, the... |
The correction question you should ask about why various operations in RC4 (or, for that matter, any other cipher) are there would be "if I were to remove that, what would the impact be? Would this weaken the cipher in some way?"
At your current state of knowledge, that may be a rather imponderable question, but it... |
**Yes**, that omission weakens the cipher: the output $\mathtt K$ has a short cycle (at most 65280 bytes) for a sizable class of keys (one in 65536). The following details why.
Because earlier code leaves $\mathtt i=256$ and the first execution of `i := (i + 1) mod 256` makes that equivalent to $\mathtt i=0$, not i... |
I'll port the [contents of the link of Henrick](http://books.google.com/books?id=0hQvhwk7xkwC&pg=PA111&lpg=PA111&dq=nist+oiw&source=bl&ots=58dl2T9aq5&sig=q1uz5sUsE7qya9svlz62DmPq2ZA&hl=en&us=X&ei=KswuVN3eJYW_ywPZ04CwCA&ved=0CEoQ6AEwBw#v=onepage&q=nist%20oiw&f=false):
> Within the United States, one key forum for pro... |
I am a programmer, so when I hear `XOR`, I think about the bitwise operator (e.g. `0110 ^ 1110 = 1000`).
The mention of "XOR" comes up quite a bit in cryptography. Is this the same XOR as the bitwise operator? If so, how is it used to encrypt a large amount of data rather than just an integer? Wouldn't you need the ... |
How is XOR used for encryption? |
Consider the values $a$ and $b$ are encrypted as $c_1=(a \oplus D)$ and $c_2=(b \oplus D)$.
My question is: can we derive $b+a$ from any combination of $c_1$ and $c_2$?
Note:
1. I admit that the $D$ should have not been used for both $a$ and $b$. For now assume we can use it.
2. Basically I define the val... |
I've looked up RC4 algorithm and it's seems easy enough but some parts of it seem random to me.
In the key schedule part take for example the following part :
j = (j + S[i] + key[i % keylen]) % 256
I can understand most of it:
- the `key[i % keylen]` is padding in-case that the key is shorter than 256 byt... |
I understand that with more encryption rounds the more complex the ciphertext becomes due to multiple substitutions and permutations. What I don't understand is the purpose of these features.
I am under the impression that key length and the number of subkeys are the dominant factors in deciding the strength of a c... |
What benefits do substitution boxes and permutation boxes offer in DES? |
The National Institute of Standards and Technology (NIST) recommended elliptic curve domain parameters to have names such as **“secp…”** and **“sect…”**.
For example: *“**secp**224k1”* and *“**sect**571k1”*.
What is the difference between **“secp…”** and **“sect…”**? |
What is the difference between “secp…” and “sect…”? |
I am given the `q`, `p`, and `e` values for an RSA key, along with an encrypted message.
Here are those values:
p = 1090660992520643446103273789680343
q = 1162435056374824133712043309728653
e = 65537
sample ciphertext = 2996045397736918955... |
To convert a bitcoin private key to a public key the secp256k1 point multiplication math is used.
Could I, theoretically, convert a private key to a public key just using the four arithmetic operations and scalars. If not, what else would be absolutely necessary?
I want to do it using a purely mechanical engine so ... |
Could secp256k1 point multiplication...? |
To convert a bitcoin private key to a public key, the secp256k1 point multiplication math is used.
Could I – theoretically – convert a private key to a public key just using the four arithmetic operations and scalars. If not, what else would be absolutely necessary?
I want to do it using a purely mechanical engin... |
My teacher stated that the
> The number of possible keys (E) in a monoalphabetic cipher is 26!
My thinking :
> Every letter in the alphabet can be 25 different letters hence it the
> number of possible keys should be 26^25
What is wrong with my way of thinking and how did she come to a conclusion of 26! ... |
Your teacher is right, and here's why:
What happens if you encrypt A with G and B with G? You can't decipher it, because you have no idea if the G in the ciphertext was an A or a B.
So for the plaintext letter A you can use the ciphertext letter A, B, C, D, ..., Y or Z. (26 possible letters.)
For B you can use... |
Everyone is comparing bcrypt to scrypt. Bcrypt is proven, lots of cryptoanalysis and no vulnerabilities so far, but uses very low memory. While scrypt uses a lot of memory, but it's too early in its life. Is there anything problematic by using them in cascade/together? Like scrypt the password then bcrypt the result. E... |
Why don't we use bcrypt and scrypt together? |
Yes, it's the same [XOR][1]. It gets used inside most of the algorithms, or just to merge a stream cipher and the plaintext.
Everything is just bits, even text. The word "hello" is in ASCII "01101000 01100101 01101100 01101100 01101111". Just normal bits, grouped in 5 bytes. Now you can encrypt this string with a ra... |
On page 2 of this [article][1], there is example of FEAL-4.
At round 2, the input to F (Round Function) is 0x80800000. As F accepts only 4 bytes I divide the input by 2 so that (As I assume the result will be 8 bytes firstly) I compute 8080 and after 0000, concating two results will be 8 bytes:
0x8080|0000
... |
I am trying to verify the statement above. So far I only know One-Time pad is the only perfectly secure cipher. It has key length same as plaintext. I think the statement is true but I don't know how to prove it.
Can anyone give me some hints? |
I would like a data structure supporting two operations: $\mathsf{set}(k,v)$ and $\mathsf{get}(k)$, with the following properties:
1. $k$ can be any number between $0$ and something impressively large, like $2^{256}-1$.
2. If there is some $v$ such that $\mathsf{set}(k,v)$ has been called then $\mathsf{get}(k)$ ret... |
the Chi step mapping of the Keccak-f permutation in Keccak is defined to be "nonlinear mapping". Without this, the complete permutation would be linear.
What does "non linear" mean?
Page 15 in http://keccak.noekeon.org/Keccak-reference-3.0.pdf |
What does "nonlinear mapping" of Chi in Keccak sponge function mean? |
I am trying to verify the statement above. So far I only know that a One-Time-Pad is the only “perfectly secure” cipher. It has a key length which is exactly the same as the plaintext. I think the statement is true but I don't know how to prove it…
Can anyone give me some hints or point me to an according reference ... |
Page 15 of [the Keccak reference ](http://keccak.noekeon.org/Keccak-reference-3.0.pdf) (PDF) explains that the $Chi$ step mapping of the Keccak-f permutation in Keccak is defined to be “nonlinear mapping”. Without this, the complete permutation would be linear.
What does *”nonlinear”* mean?
|
What does “nonlinear mapping” mean? |
This answer builds on [the answer supplied by @otus](http://crypto.stackexchange.com/a/19271/12164). There is also an important worry about whether the main solution works at all as advertised. I am posting it now to make clearer to @otus a question I asked in a comment. I will eventually either delete it or substan... |
[This guide][1] says that for a rainbow table or pre-computed hash chain, you can only get a probability that a plaintext is in a table, not a guarantee. Is there a way to guarantee every possible plaintext (of a certain length) is in a table? My thought would be by storing entire chains and generating more chains if a... |
How to guarantee every plaintext is in a rainbow table? |
I am wondering if using Skein or the Keccak hash algorithm in this construction (as a stream cipher) is secure:
- $H$ = Keccak or Skein hash with a 256 bit output
- $K$ = The main 256 bit random key, pre-shared between sender and receiver
- $K_M$ = A secondary 256 bit random key for creating the MAC, pre-shared... |
> I am wondering if using Skein or the Keccak hash algorithm in this construction (as a stream cipher) is secure:
In the case of Skein and Keccak it should be secure. However, both of those have defined their own cipher modes which you should IMO prefer. (For speed and compatibility, if not security.)
* The Skein... |
Page 15 of [the Keccak reference ](http://keccak.noekeon.org/Keccak-reference-3.0.pdf) (PDF) explains that the $Chi$ step mapping of the Keccak-f permutation in Keccak is defined to be “nonlinear mapping”. Without this, the complete permutation would be linear.
What does *”nonlinear”* mean? The paper says that $Chi$... |
I am in the design phase of a secure chat application at the moment.
I am trying to make this as secure as possible.
The Serverprovider should not have access to the messagedata.
So my idea was the following:
I have two base keys, one AES and one RSA Key.
The AES Key is derived from a password the user enters. The... |
Is this a save implementation? |
I am in the design phase of a secure chat application at the moment. I am trying to make this as secure as possible.
The Serverprovider should not have access to the messagedata.
So my idea was the following:
- I have two base keys, one AES and one RSA Key.
- The AES Key is derived from a password the user ente... |
Is this a safe implementation? |
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