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I'd like to generate a private elliptic curve key from user input like pass phrase. Is the best way to do this with a key derivation function like PBKDF2? Is there a better way?
Edit (based upon @poncho's questions)
To be specific, this is for a Bitcoin ECC private key. It seems to me that if a user picks a passphrase ... |
OMAC/CMAC only specifies constants for 64-bit (0x1B) and 128-bit (0x87) block size. I would like to know how to get constants for other block sizes.
http://en.wikipedia.org/wiki/CMAC says it "is the non-leading coefficients of the lexicographically first irreducible degree-b binary polynomial with the minimal number of... |
In the Rabin cryptosystem, decrypting a message can produce four different outputs, of which only one is the correct plaintext. How can one know which of the outputs is the correct one?
|
All of the SHA-3 finalists discussed speed and efficiency of a hardware implementation of their algorithms. How relevant are such details?
I'm curious about who commercializes hardware that implements specific hashing algorithms, and who uses them. In what situations is this worth a dedicated chip, vs. just running it ... |
Is CBC with Ciphertext Stealing (CTS) considerably weaker than CBC with padding such as PKCS7?
I would imagine the most common situation where CTS is necessary would be due to some size constraint of an existing system, and redesign of the system is inconvenient. So, while it clearly reveals the length of the encrypted... |
I created my PGP key in 2000. I’ve revoked the older, weaker sub-keys in favor of a 4096-bit RSA one, but the primary key is 1024-bit DSA. I read on Wikipedia that…
NIST 800-57 recommends lengths of 2048 for keys with security lifetimes extending beyond 2010.
Should I consider my primary key insecure?
If so, is the... |
How could the following scheme be made more resilient to attacks capable of utilizing massive amounts of resources?
Assume all random values are cryptographically secure.
Key derivation: scrypt using a random 16 byte nonce. The work factor is 1048576 which takes a GB of memory and ~3 seconds to compute on a 2500k.
Auth... |
In a hypothetical discussion we ended up with a concrete question I'd like to find the answer to:
If you try to brute force an RSA encryption, but the original vale which was encrypted was just random binary data, can you ever be sure you found the correct key? In other words: What are the success criteria for RSA brut... |
I'm trying to understand the math outlined in this paper on a RSA signature forgery attack. I understand it except for one aspect of how the cube root (that makes the forged signature) is computed.
On page 8, it's shown that this expression (the forged block that needs to be cube-rooted):
$\sqrt[3]{2^{3057} - N*2^{2072... |
I understand how the RSA algorithm works for encryption and decryption purposes but I don't get how signing is done.
Here's what I (think) I know and is common practice:
If I have a message that I want to sign, I don't sign the message itself but I create a hash of it and then sign that hash by using my private key.
T... |
We are in the processing to understand if our software applications is FIPS 140-2 compliant or not. Currently in our application, we are using our own implementation of AES algorithm. AES is a FIPS 140-2 compliant algorithm.
The question would be whether this would render our app not FIPS 140-2 compliant since we are... |
In the NSA's document, "The Case for Elliptic Curve Cryptography" (archived), we have
+---------------+-------------------------+-----------------+
| Symmetric Key | RSA and Diffie-Hellman | Elliptic Curve |
| Size (bits) | Key Size (bits) | Key Size (bits) |
+---------------+-------------------------+----... |
What is the current standard of random bit generators? RSA relies on two large prime numbers, and I am wondering what is the algorithm used to generate such numbers?
|
Suppose I implement RSA myself in C and I use just the formulas from number theory. What attacks would my implementation be vulnerable to? Can anyone explain this to me like I'm 5?
|
The answerer has commented that scrypt's memory use is "only a function of r". $\:$ However, he has
not addressed my argument that it also depends on N, in one of my comments from over 5 days ago.
I had somehow gotten the impression that scrypt offered a separate memory-factor in addition
to its main work-factor. $\... |
After saw the xkcd comic Self-Description, I wonder if it is theoretically possible to construct a self-descriptive string that contains its own hash value?
Let's say the string's MD5 value is 663ef7d3f38cf900574cd4d9f83eb1b7, the string would be something like:
...
The md5sum value of this file is 663ef7d3f38cf900574c... |
Edited (I removed the emphasize on Integers):
My question is partly cryptography and partly programming, I would appreciate any help on any aspect of it :)
I want to use PBC library to do the following operations:
Create a finite group, with "my custom" order ($Z_q$).
Choose a random value $g$ from this group.
Compute... |
From Wikipedia I read that the IV is used to randomise the mapping of cleartext to cipher text and that the IV is usually stored (in cleartext) together with the encrypted record. (http://en.wikipedia.org/wiki/Initialization_vector)
However if I look at a specific implementation in C# when deriving the key using Rfc289... |
Hopefully this question is not too simple - I did some research but with encryption I really don't want to make a mistake.
Our scenario is that multiple groups need to encrypt a number and arrive at the same result.
This is because they want to use credit card numbers to search for documents, but we are only willing t... |
In the IETF RFC draft named "SM2 Digital Signature Algorithm" a signature algorithm is specified. The RFC does however not mention why this signature algorithm has been defined. Nor does it specify what the advantages of this scheme are over ECDSA. It seems that SM2 is the preferred EC signature format in China.
So the... |
I have calculated the average number of operations in 1 round of SHA-256 as follows:
Additions: 9.25
Bitwise Rotations: 9
Bitwise Shifts: 1.5
Bitwise AND: 5
Bitwise XOR: 10
I have certain proposals that save the following number of operations in one SHA256 evaluation (i.e. 64 rounds) for Bitcoin mining:
Ad... |
Can somebody explain what the "shared secret" and "password" do when opening/creating a VPN tunnel?
In this specific case I setup a VPN to my Fritz!Box and I had to provide a shared secret (which was pregenerated and very long) and a password.
I'd like to understand how each of these two credentials is used in terms of... |
I'm looking for references, papers or guidance on a class of system which I have not seen widely discussed.
Consider powerful electronic machinery which remains in the custody of communicating parties, is reasonably insulated from tempest-style attacks, and which is not networked. Between tasks its state is completely ... |
Let $G_1, G_2$ be additive groups and $G_T$ a multiplicative group, all of prime order $p$. Let $P $ in $G_1, Q $ in $G_2$ be generators of $G_1$ and $G_2$ respectively.
A pairing is a map:
$e:( G_1, G_2 )-->G_T $
can anyone explain it?
|
Assume that there are three users, each with their own secret key $d_i$ and the corresponding public key $Q_i = d_i \cdot P$, such that $Q_i$ is a point on an elliptic curve and $P$ is a base point on this elliptic curve.
Is $d_1 \cdot Q_2 \cdot Q_3$ equal to $d_2 \cdot Q_1 \cdot Q_3$ or $d_3 \cdot Q_1 \cdot Q_2$?
How ... |
It seems to be possible to retrieve the (public) key used for creating an ECDSA signature just from the signature alone.
This seems like an interesting property; as far as I know, RSA doesn't share it.
Depending on the application, this can both be an advantage (shorter messages, as the public key or a key id doesn't h... |
Keepass is a well known open-source password manager program, with plugin support. One of the offered plugin is a twofish encryption mode of operation in lieu of the build-in AES algorithm (http://keepass.info/plugins.html#twofishcipher).
Since I am fond of the xfish cipher family, I looked at the source of that plug... |
Given a message $M$ and a cryptographic hash function $H$, let $f(M) = E_K(M || H(M))$ where $E_K$ is AES-128-CBC encryption with PKCS#5 padding. Take $H = \textrm{SHA-256}$ if it matters. In other words, we encrypt the message and a hash of the message, with CBC.
Does $f$ guarantee the authenticity of the message? (As... |
It would seem to a naive eye that if you have a MAC, you have a hash function: use a key that all the parties know (such as all-bits-zero).
A potential application would be a resource-constrained platform where code size is at a premium, and which needs to implement AES for confidentiality: instead of also implementing... |
I am using an algorithm (can be found here1) that can compute efficiently the GCD of multiple RSA keys. It intended for RSA keys that were generated with low entropy and may have one of their primes in common.
In the documentation it is stated that:
if a modulus shares both of its prime factors with two other disti... |
I'm using the Crypto++ implementation of Salsa20 for a software project we are working on and I'd like to know if there are any SSE or software optimizations that will increase the speed of the CSPNG?
|
Its believed that the quadratic residue modulo $n=p·q$ for large primes $p$ and $q$ is intractable, which forms the basis of some cryptosystems.
However, it is solvable if the factors of $n$ are know, such that the problem modulo a prime is easy (we use the Chinese reminder theorem) to simultaneously solve the problem ... |
Symmetric encryption schemes such as AES have known security levels equal to their key sizes (i.e. breaking an encryption with an $n$ bit key needs about $2^n$ work steps). Elliptic curve encryption gets halfway towards optimal: its security is half the size of the public key.
Are there any public key encryption schem... |
Assume d is a 128 bit random integer and P is base point of an elliptic curve and Q = dP is a point on the elliptic curve and SHA is a hash function with 128 bit output, my question is:
Is size Q equal to size SHA(Q)?
If not, then wich is smaller size?
|
If an adversary holds thousands of encrypted files that were encrypted with the same cipher, can he determine which cipher method had been used on the files?
Assume that the adversary has no prior knowledge about the encryption environment.
Details:
Let's say I have a encryption program that allows me to select 1 out o... |
Typically，I think latency should mean the time from the first plaintext input to the first ciphertext output, when the block cipher is not totally unrolled (such as AES unrolled with 2 rounds).
If I use a pipeline to increase the throughput, the latency should relate to the amount of pipelined data. E.g. with AES unrol... |
I have an application written in C, running in Linux. It uses IPsec (ESP) (manually putting the IPSec packet together) to send certain packets. The algorithm used for encrypting the payload is 3DES-CBC (using Libgcrypt).
So my doubts are regarding the IV that I have to use. For this scheme to be secure:
Is it enough to... |
I found a program which takes a purely alphabetical message, converts the letters to their ASCII values and combines them with the ASCII values of an alphabetical key (wrapping around when it gets to Z).
(The key being used is fully random and is required to be at least a long as the message.)
But from what I usually r... |
Where does the word or acronym Keccak come from?
Guido Bertoni, Joan Daemen, Michael Peeters, and Gilles Van Assche. Keccak sponge function family main document. Submission to NIST (updated), 2009.
"NIST Selects Winner of Secure Hash Algorithm (SHA-3) Competition". NIST 10/2/2012.
|
I'm attempting to implement multiplication and division in $GF(2^8)$ using log and exponential tables. I'm using the exponent of 3 as my generator, using instructions from here.
However I'm having trouble getting the expected answer for some of these trivial multiplications.
For $2 · 4$ this works:
$$ \begin{align*}
... |
I am reading the paper Software Protection and Simulation on Oblivious RAMs by Oded Goldreich and Rafail Ostrovsky. And I wonder about the description of the "Square Root" solution of oblivious RAM simulation at page 20.
The algorithm seems simple: the aim is to 'simluate' the original RAM of size $m$ by an oblivious ... |
I'm working with openssl cryptographic libraries, I'm new to all these cryptographic stuffs and slowly I'm learning all these. I have a doubt regarding random number generator, I'm using RAND_pseudo_bytes() for generating a pseudo random number. I'm providing a seed to it with my required entropy. But my doubt is if we... |
I'm using Lagrange's Interpolation technique to reconstruct the secret from a set of point pairs (x,y).
Since I only need the secret, not the whole polynomial, I have simplified the reconstruction process as follows:
Let Secret $D = 10$, and we use a 3 out of 3 secret sharing scheme which generates 3 key pairs
a... |
I gather, from reading the GPG manual, that symmetric encryption based on a password uses one of a variety of Key Derivation Functions (KDF). Although not explicitly mentioned I assume that PBKDF2 is the default as the other options appear to be legacy algorithms from the PGP standard.
However I can't find any informat... |
I've searched some information on ECC, but so far I have only found Diffie-Hellman key-exchange implementations using ECC, but I don't want to exchange keys, I want to encrypt & decrypt data like in ElGamal.
I know that ElGamal with elliptic curves should be possible (Since ElGamal is based on DH), but I have no idea h... |
I've stumbled (jobwise) over a system where small messages (512 Bytes or less) are encrypted and decrypted using a simple XOR using a OTP. That OTP is created using a seed based on the individual user passwords and a simple PRNG.
I'm currently seeing the following problem: Alice always keeps her password absolutely sec... |
Can somebody explain (or point to a reference) why the Schnorr protocol cannot be proved zero knowledge?
|
When dealing with cryptographic data, is there a chance that attacker recovers portion of data I used in my program? Should I try to delete every bit of keys and encrypted data that I used, overwrite it with zeroes?
And one extra, how is situation different in languages with garbage collection like Python or Java?
|
Round 16 on the encryption side, and round 16 on the decryption side of DES have no swapping module.
Why is it like this? Can anyone provide any justification?
This is my homework question.
|
The requirement is to authenticate 1000s of devices to a server when the devices try to contact the server. The problem I face is that all authentication protocols require some kind of shared secret between the devices and the server. And for devices to know this shared secret, some reliable user has to manually enter ... |
A system fell into my neck, where lots of files are splitted into several segments and encoded via RC4. RC4, because client side - slow computer, slow flash arithmetic ops - can only decode big blobs with this simple algo in a reasonable amount of time. I have some reservations regarding the RC4 security, so I'd like t... |
I just read the presentation slides of John M. Kesley (from NIST) for his invited talk at CHES 2013 about SHA-3 and learned that NIST is going to standardize Keccak with a possibly modified padding scheme. Ok, so far so good. But what I don't understand is why they thought it was a good idea to limit the possible capac... |
Is there a function or system which is time depending in which the effort required to brute force the decryption increases with time? It is easy to break encryption from many years ago because computers are so much faster. Is there a system in which time is a component and as time passes then it gets harder & harder to... |
How does a cracker know if they've broken CBC or stream encryption? With hashe cracking one would know because you have the password that you started with to test. But for CBC decryption, you have a 16 bit block (AES), a key, and an IV. With the wrong key one will get random data as output. So how will one know when th... |
I'm reading patent application US 20120278897 A1 — “System and method of sort-order preserving tokenization”. Near the bottom they describe their token generation algorithm, which basically involves using the first few characters of a string as input to a modified order preserving Ziv-Lempel compression function descri... |
The keepass password manager uses multiple rounds of AES for its key derivation, as described here. I was somewhat surprised that it wasn't using pbkdf2, bcrypt, or something more common. Essentially, the key derivation is:
key = sha256(password)
cipher = AES(random_seed1, ECB)
for i in number_of_iterations:
key = ... |
I understand modular arithmetic(or at least I think I do!) and I've tried to read and learn about how the Math in RSA works(and I think it went pretty well). I've been reading up on ECC and it looks very interesting and I tried solving a few basic math problems that involve ECC. I understand the basics, now I'm trying ... |
In traditional DH one chooses two shared parameters: a large prime $p$ and base $g$, which is primitive root $\bmod p$. Suppose that the generation algorithm is broken and $g$ generates only a subgroup (the group with fewer elements than the number of coprimes to $p$), what could be the possible attack? what's the comp... |
The Wikipedia article "One-time pad ~ Authentication" says :
For example, an attacker who knows that the message contains "meet jane and me tomorrow at three thirty pm" at a particular point can replace that content by any other content of exactly the same length, such as "three thirty meeting is cancelled, stay home"... |
I know that the HMAC is a message authentication code that uses a cryptographic key in conjunction with a hash function (SHA1 , MD5, etc.). The HMAC output is 160 bits for HMAC-SHA160 and 256 bits for HMAC-SHA256 bits that can be truncated according to the intented application. My quesion is about input...
What is the ... |
When analyzing a repeating-key xor cipher to find the key length, I've read about two key methods (assuming there aren't just repeating chunks of ciphertext for Kasiski's method), for some assumed key length $l$, checking the Hamming distance of nearby chunks of ciphertext of length $l$, and checking the IoC for column... |
Let's say there is a piece of software that uses AES CTR to encrypt different messages using the same key but with slightly different IVs.
So for example, a 16 byte IV, the 2nd 8 bytes are always the same, but the 1st 8 bytes are random.
How insecure is this?
I know that you shouldn't use the same IV and key. But do ... |
Let's suppose we are using the exponential ElGamal as a public-key encryption scheme, so that we encrypt $g^m$ instead of $m$, for some generator $g$. Let $x$ be the private key, and $h=g^x$ be the public key.
We have two parties, and each one of them has a ciphertext encrypted with the same public key: $(R_1,S_1)=(g^... |
When sending a block to be decrypted or encrypted, with RijndaelCBC, we input the data to decrypt/encrypt and an IV for syncing and to prevent identical outputs for identical inputs.
This question is regarding to any loopback mode use of AES chipher block using an IV, but my experience is with CBC.
Inside the RijndaelC... |
The universal composability allows one to the analyze security of cryptographic protocols . But it does have some gaps when it comes to analyzing few protocols especially two party cases when there is no honest majority players
Now when it comes to protocols designed for cloud computing, where few parties outsource co... |
I am studying LogSpace Merkle Tree Traversal algorithm in "Post Quantum Cryptography". I don't understand the Table 1 on page 58.
My question is: Why within of the $2^h$ rounds for $NEED_h$ exist only one $TAIL$, if tail in the page 42 is defined than intermediate nodes in $STACK_h$?
Algorithm 2.1 Treehash
Input: Hei... |
I would like to know what is the security of an encrypt-and-MAC with different keys for each transaction
For example: the one-time-pad with $k_1$ and the HMAC with $k_2$
$$C = M \oplus k_1\\
MAC = HMAC(k_2,M)$$
The ciphertext is $C||MAC$. The two keys $k_1$ and $k_2$ change for each transaction (for each $M$).
|
I am researching vulnerable RSA moduli which are composed of primes generated with poor entropy. Having a list of these primes I searched for variable sized repeated patterns among them and I noticed the following:
DD93536E58A60B0F56BF95FAEDC7CA42A9C9809A0AAE2FC971C3D9963587ABCEAF2BAB479A68DDC9EFF0E98F0F5FD488A9DD08CC... |
In some protocols, a key is derived from a hash of many parameters (K=H(param1,param2,param3))
Is there a hash function that takes many parameters as input ?
Or we can simply use a function like SHA-1 by concatenating these parameters as input ?
|
According to PKCS#11 v2.20, "C_GetMechanismInfo obtains information about a particular mechanism possibly supported by a token." Does that mean C_GetMechanismInfo() can return CKR_OK on a temporarily disabled mechanism? For example, if C_GetMechanismList() does not return CKM_MD5 in the result then is it OK for C_GetMe... |
In regards to meet in the middle type attacks, I have been considering the amount of operations in order to successfully find a key given two sets of plaintext / ciphertext pairs. All of the sources I have checked have stated that the maximum number of trials that are needed is $2^{n+1}$, however this does not seem to ... |
What is the ASN.1 OID associated to bcrypt (the key derivation scheme)?
For instance, PBKDF2 has 1.2.840.113549.1.5.12 and it is therefore possible to store a private key in a PKCS#8 structure, encrypted with a password. Is that possible with bcrypt?
|
Dave here, with a plan for storing secrets.
Threat model:
Database and keyfile may (will?) be stored on un-trusted servers.
Database contains many valuable secrets (passwords), encrypted by key stored in keyfile.
Source code is public.
Keyfile and database SHOULD never be stored on the same server, but will always ne... |
Preamble
Before I ask this question, please accept that I fully understand that 'rolling your own' is never a good idea, and that I am a relative n00b. The only reason I am doing this the way I am is that there are major constraints - I have no high-level crypto libraries (like, say, NaCl) available, and this will run ... |
Why is the complexity of RSA-1024 80 bit and not 86.76611925028119 bit?
Here is the complexity for the GNFS (pulled from the linked Wikipedia
article):
$$\exp\left( \left(\sqrt[3]{\frac{64}{9}} + o(1)\right)(\ln n)^{\frac{1}{3}}(\ln \ln n)^{\frac{2}{3}}\right)$$
where $n$ is a number to factor. Evaluating the above ... |
(Originally posted to SOF, but I got no answers)
I am designing a small application for use inside my company. My application needs to connect to a third party website on behalf of my application user. I would like to safely store the user's credentials for the third party site in my database. Obviously, storing the th... |
I do not really understand the meaning of a "trapdoor" in cryptography, so here are my questions:
What is the meaning of trapdoor and how can I convert a word or string using a trapdoor in cryptography?
Is a hash function considered to be a trapdoor function, or is a trapdoor function some kind of encryption?
What i... |
Diving into the history and evolution of the Message-Digest algorithm by Ronald Rivest, I have been able to track back papers from MD6 down to MD2. Yet, somehow I can not seem to be able to find any papers, specifications or even the slightest indications of MD1.
As the numbering (MD2, MD4, MD5, MD6) seems to be a cons... |
I'm playing around with a package that does Elliptic Curve Cryptography from http://jecc.sourceforge.net/
Every time I encrypt a value it produced a different result (same private key). However I'm always able to decrypt this result with the related public key. For a 1 byte result the resulting data is 34 bytes, 2 byte... |
I tried out the paper/pencil explanation here, and it seemed to make sense just fine until I came to decryption. Here is what I worked out:
Key Creation:
Choose two different prime numbers p and k:
p = 23
k = 29
Find n by calculating p * q:
n = 23 * 29
n = 667
Find z by calculating (p - 1) * (q - 1):
z = (23 - 1) * (... |
I read that hash chaining can be used to prevent hash collisions, while the chosen prefix attack allows hash collisions for algorithms like MD5.
How are they related? Does hash chaining prevent the chosen prefix attack?
|
So I was thinking about variations on the Dining Cryptographers problem - In some cases, it's useful to be able to post a message without revealing the source, but with the additional constraint of not revealing the entire group to one another.
For instance -
Let's say you have 20 members in a ring.
Each single member... |
Can we use symmetric-key algorithms without an initialization vector?
I am making an app where both the sender and receiver share a key and there is no way to create an initialization vector for each encryption. So I was thinking about setting the initialization vector to NULL while encrypting. Am I allowed to set the ... |
Assume the case, that two participants have agreed on a key $K=g^{ab} \mod p$ via Diffie Hellman. I have the need to change the key every now and then. The first idea I had was to simply initiate a new agreement, so both chose another exponent, so the new key would be $K'=g^{a'b'}\mod p$.
I wonder if it would be also ... |
I am trying to do some elliptic curve calculations by hand, just to refresh myself on how the system works. I calculated some points and did some operations by hand. I am trying to double check my work with some web calculators, but I have tried several different calculators and each gives me a different result...
Is t... |
I understand the the texts within the Voynich Manuscript are of an unknown language, and yet cryptographers are still working on it and still trying to decipher it. Does that mean that it is possible to crack any piece of writing even if it's in a language you don't know, and assuming you have no access to any tools th... |
I'm working on a little personal project where security is very important, and I've thought for a while about the best way to do this. Now I am looking for a little outside help on good practices. The goal is to store personal text data on a server (like wifi passwords, etc) and be obtained through a password. I wanted... |
All examples of one-way functions I have see till now are closely related to the assumption that $NP\neq P $ (or even weaker ones, such as $UP\neq P$), but why not considering the theorem $P\neq EXP$?
In particular, why not building functions that in one way are in the class $FP$ and the inverse function computable in... |
Suppose two parties want to communicate securely with each other (Bob and Alice) using a simple messaging system in English. There are approximately 180,000 currently used words in the English language.
The protocol
Bob creates a random private key of 512 bits in length e.g. 2fba5541fda58c643524cb629cb310674d029d7dd68... |
I've been familiarizing myself with the basics of PGP. If I understand correctly, PGP symmetrically encrypts the data of interest using a random single-use key, then encrypts the encrypted data and its symmetric key using the public key of the intended recipient.
What benefit does the inner layer of symmetric key encry... |
Using RSA public key (n,e) the encryption of a message is
c= (m^e) mod n
and the corresponding message is decrypted as
m = (c^d) mod n
How does the RSAES-OAEP algorithm specified in PKSC#1 v2.1 differ from the above basic method?
Is it possible to decrypt a text encrypted using RSA PCKS1 v2.1 RSAES-OAEP algorithm w... |
I was reading up on PBKDF2 and noted the following:
DK = PBKDF2(PRF, Password, Salt, c, dkLen)
PRF is a keyed HMAC, but I can't seem to find out what they use as key for the HMAC?
|
I am trying to design MiTM protected key exchange algorithm.
For instance I am using RSA asymmetric keys.
Alice and Bob respectively have each their own pair of keys. And they should be able to exchange public keys. In real life implementation there would be a relay 3rd party which should only allow Alice and Bob excha... |
I don't understand what an active s-box is (in reference of design criteria 8 of the DES).
Because according to DES, all 8 s-boxes are used every round. But this is not what active means.
So my question: What is an active S-Box, and what does it mean when an s-box is active (or when two or three s-boxes are active)?
|
So let's say you had infinite time and energy. You have a hashed string of some sort. Because you have infinite time and energy, you can produce a collision(or the original value) easily enough. But, there is a problem. The hashed string was hashed an unknown amount of times. (ie, it may have been produced by sha256(sh... |
I want to sync blobs over the network and the most frequent change will be appending to blob. To minimize data amount sent I would prefer to encrypt appended data, send it over the network, append to encrypted blob and then decrypt whole blob at once when needed. Changes are very frequent and small, so storing each cha... |
The recent revelations that airport staff can detain travellers in an interrogation room and force them to give over passwords to encrypted-HDD laptops under threat of jail time has made me think about some sort of dual password encryption/decryption mechanism.
For example:
Password 1 decrypts all the data as usual.
P... |
Recent news articles have suggested that the NSA may be involved in trying to influence the cryptography in public standards or commercially deployed software, to enable the NSA to decrypt the encrypted traffic. For example, see this article in the New York Times.
The New York Times article specifically mentions a 200... |
Threshold decryption of public-key encryption schemes allows the decryption key to be distributed among trustees. Then, to decrypt the ciphertext it requires at least threshold t trustees to run the decryption protocol in order to get the plain text.
Now, most of the literature is either based on generic multiparty com... |
Are there any proofs that cryptographic functions on an elliptic curve are any more difficult than the analogues over modulo arithmetic?
While at present, ECC appears to be more difficult, as it is not as advanced as research into RSA etc., it seems to me there should be no reason why ECC is much stronger than, say, RS... |
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