1
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1answer
664 views

Why are RSA keys encoded with ASN.1 for TLS?

Browser vendors use ASN.1 encoding for RSA certificates in the TLS protocol. RSA public keys are just a number, so why do we need encode them to something else? That increases the risk of security ...
1
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3answers
585 views

File encryption with one keypair?

I'm working on a program that uses an ECC keypair in a (password protected) PKCS12 file (.pfx) to encrypt files. I like this method because I think it will be higher security (using ECDH to negotiate ...
1
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1answer
301 views

Is there a problem with constructing a CSPRNG using MD5 or SHA1?

Is there any security concerns with building a CSPRNG using a broken hash function like MD5 or SHA1? The design is such that a CRC-like function is used for mixing entropy and MD5 is used as the ...
1
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2answers
339 views

Generate random number which should depend on key

i want to generate random number for example from [1..100]. The algorithm which would generates random number should work similarly like a "Linear congruential generator", like this: $X_{n+1}≡(aX_n +...
1
vote
1answer
137 views

Needing to encrypt plain sight information

Okay here are my requirements. I need a solution that can do the following. Lets say I have an encrypted piece of text with the value "20". and I have UserA and UserB I give UserA the Keys (/5 and ...
1
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2answers
162 views

Contruct a protocol to determine if three secret keys are different, without revealing any of them?

I am trying to find a protocol for this problem: Three persons, $A$, $B$, and $C$, know secret numbers $s_{A}, s_{B}$, and $s_{C}$, respectively. They want to know whether their numbers are all ...
1
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2answers
162 views

What is an easy method of proving that a cryptographic oracle attack is possible?

Lets say an application is using CBC mode without authentication. The application is generating cipher text. This cipher text can be manipulated by the attacker and then transmitted back to the ...
1
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1answer
205 views

Crack cryptographic hash functions using Toffoli gates?

Might it be possible that reversible combinatorial circuits (or some emulating software) are going to be used to get the input of the white box? I mean if I have constructed a proper reversible ...
1
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2answers
178 views

Encryption algorithm which produces comparable results for substrings

I am wondering is there any encryption algorithm available which produces comparable string. I am expecting the output as shown below. ...
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2answers
196 views

why $e(g,g)^N=1$ in bilinear pairings holds?

I can't get the point of prime order bilinear pairings:$\mathbb{G}\times\mathbb{G}\rightarrow\mathbb{G}_T$,$g=$ generator of $\mathbb{G}$ , $N=p*q$, $p$ and $q$ primes and $e(g,g)^N=1$. why $e(g,g)^N=...
1
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1answer
931 views

How to jusify {e,n} is a valid RSA public key?

I have a two set of key {36,77} and {50,117}, How can validate if it is a valid RSA public keys? Is there any simple method?
1
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1answer
330 views

Are there any multiparty homomorphic encryption schemes?

Are there any multiparty homomorphic encryption schemes ? Most of the literature is about two party schemes . Is there any generalization made for n party ?
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3answers
300 views

Should I use md5 for my new application?

MD5 is a very fast hash and its output is short and easy to store. Should I use it for my non-security-sensitive application? I don't think so, but I can't seem to convince anyone else that this is ...
1
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2answers
347 views

Relation between Threshold Cryptosystem and Secure Multiparty Computation ?

Is there any relation between secure multiparty computation and threshold cryptosystem ?
1
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1answer
1k views

What is the correct value for “certainty” in RSA key pair generation?

I'm creating an RSA key pair in Bouncy Castle and need to specify an int value for certainty. This Stack Overflow answer says it is a relative test for how prime the values are. There is another ...
1
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1answer
4k views

Removing Padded Value in Decrypted Message

How to remove padded value in Decrypted Message? I am using AES Algorithm. Let's take this as the decrypted message: "abcdefghijklmn " There is a 2 space in ...
1
vote
2answers
128 views

How can I protect against the failure of a block or symmetric cipher?

Can I protect against the failure of a block or symmetric cipher by chaining different techniques together? If so what implementation details should I be aware of? Are some combination of ciphers ...
1
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1answer
216 views

RSA/DSA: Wouldn't it make sense to sign using decoding the data hash?

Why is encoding using the private key used for signing? Wouldn't it make sense to keep the premise, that private is for decoding and public is for encoding? i.e. create a hash and threat it as a ...
1
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2answers
158 views

Standard symbol / notation for “x knows y”, or the inverse

What's the standard way to express "$x$ knows about $y$", or "$x$ has no knowledge of $y$" in cryptographic notation? Example (PRNG predictor): $\exists f : P(f(G(k)|_{0..n}) = G(k)|_{n+1}) \geq 0.5 ...
1
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2answers
354 views

One-way function and factoring

I am confused about the hardness of the one-way function behind cryptography -- if someone could factor the large number produced back into two primes quickly then the one-way function would be broken?...
1
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2answers
304 views

Factoring a polynomial over a GF [closed]

I have the following question: What polynomial, when factored over the field $GF (2^8)$ based on the irreducible polynomial that is used in Rijndael, will factor into all the polynomials in the ...
1
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1answer
361 views

Verifying the integrity of ciphertext using the cleartext hash?

I want to be able to verify the integrity of a ciphertext by providing the cleartext hash, for this to work it would need to: $$hash(crypt(cleartext)) = f(hash(cleartext))$$ Where $f$ is an ...
1
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1answer
1k views

The use of cribs [closed]

I'm looking to incorporate more crib usage in breaking ciphers in unknown enciphering schemes, or at least to gleam what information I may. This seems to be a big hurdle to me, and I'm looking for ...
1
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2answers
66 views

How to design a balanced LFSR with period 1023 and linear span 55?

I am trying various combination of LFSR's to try to design sequence of period 1023. The linear span should be 55 and the output 1023 bits has to be balanced. I have tried with five LFSR's with degree ...
1
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1answer
42 views

Clarification on Key exchange approaches in TLS/SSL

When RSA is used for key exchange in SSL, the client basically encrypts some random data using the server's public key and and sends it to the server. This data is then used to compute the shared key ...
1
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1answer
61 views

HMAC vs CMAC, which is faster?

I want to know which is faster-HMAC or CMAC.I know CMAC is based on block cipher encryption,where output of each block is X-OR with the next plain text block. If security is not a concern,which will ...
1
vote
1answer
28 views

RSA I2OSP & OS2IP in RSAPSS verification

I started working with RSA two weeks ago. But I coudn't really understand how exactly I2OSP & OS2IP are working. I am using some open source for signature verification through RSA PSS algo. I am ...
1
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2answers
49 views

Layman's description of the padding oracle attack

I understand that the MAC-then-encrypt approach is susceptible to several attacks including the so called padding oracle attack. I understand that in this attack the attacker modifies the padding and ...
1
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4answers
109 views

Is this an effective obfuscation technique?

Long ago I created a simple program which obfuscated a file by taking the first byte, then XORing it with the second, taking the (original) 2nd byte and X-ORing with the 3rd, etc, down the line. The ...
1
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1answer
31 views

Size of Pre-Master Secret?

I am implementing TLS 1.2 and using cipher ECDHE_RSA_WITH_AES_128_GCM_SHA256 According to RFC 5346 Section 8.1 length of premaster secret will vary depending on key exchange method. So, what is the ...
1
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1answer
91 views

Fully Homomorphic Encryption over the Integers with Shorter Public Keys [closed]

I want to implement Homomorphic scheme from the paper Fully Homomorphic Encryption over the Integers with Shorter Public Keys. I successfully implemented key generation by taking $\lambda = 2, \beta =...
1
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1answer
71 views

Scalar Multiplication for Elliptic Curve

Let $\mathbb{E}$ be the elliptic curve $y^2 = x^3 + 6x \text{ mod } 11$ and consider the point $P = (2, 3)$ on it. How do I compute $3P$? I have been able to figure out what $2P$ is, $2P = (5,10)$. ...
1
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1answer
26 views

Can a compressed checksum be considered unique

I'm kind of guessing that the answer may be no. Since the compression is trying to reduce the output size using various optimization methods, this may cancel the properties of a hash algorithm. But ...
1
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2answers
115 views

Appropriate scrypt parameters when generating an scrypt hash

What values for CPU, memory and parallel difficulty should be used when generating an scrypt hash? i.e. ...
1
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1answer
441 views

What is the random tape?

I am reading the paper "Toward plaintext-aware public-key encryption without random oracles" by Bellare and Palacio. So I can't understand what is the tape and random tape?
1
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1answer
34 views

Why does Carter-Wegman MAC have 2n-bit output?

The Coursera course on Cryptography 1 has a section about Carter-Wegman MAC. Here is the image of slide: Now my question is both $F$ and $S$ output $n$-bit strings. We XOR two $n$-bit strings and we ...
1
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1answer
43 views

Access control problem in oblivious transfer

I am not sure whether the title is proper or not, but this question comes to my mind when I was reading $k-n$ oblivious transfers. In a $k-n$ oblivious transfer (OT) protocol, a party A has $n$ ...
1
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1answer
55 views

How is the base64 encoded signature in Craig Wright's proof constructed?

Mr. Craig S. Wright might be Satoshi Nakamoto - the inventor of bitcoin. He is currently proving the case. But how is the base64 encoded proof, that is published by himself on his blog post ...
1
vote
1answer
62 views

How do attacks on WEP work?

There is an abundance of tools and tutorials on how to break WEP encryption. However, I fail to find a nice resource that gives a clear break-down of why the attacks are possible. For example, I know ...
1
vote
1answer
74 views

How is decryption done in AES CTR mode?

Since AES CTR mode uses a unique IV and counter to produce the key to XOR with the plain text to get the ciphertext, the question is so as to how decryption is done. Since AES CTR produces a ...
1
vote
1answer
77 views

SHA256(RsaPrivateKey) == AES key?

I have an RSA private key (more specifically, an SSH key in Putty format, 4096bit) and want to use its SHA256 hash as an AES256 key, instead of using an independent newly generated AES key. Are ...
1
vote
1answer
88 views

Homomorphic Encryption or not

I am a beginner to homomorphic encryption scheme. As far as I think, it is just a kind of concealing real value without using standard encryption algorithms such as AES,DES or RSA. For example , for ...
1
vote
1answer
55 views

Disk encryption using AES-CBC: is reliance on previous block data a downside?

I have seen drives that boast that they use AES with CBC mode, which doesn't really make sense in my opinion, sure it's more secure than ECB (but actually, leaving security aside, ECB is better suited ...
1
vote
1answer
47 views

McEliece variants that support signatures

Besides the Niederreiter cryptosystem, are there any other variants that support digital signatures? Can any of them sign arbitrary signatures unlike the Niederreiter cryptosystem? What are the key ...
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, ...
1
vote
1answer
91 views

Shamir secret sharing: calculate rest of shares when you know secret and one share

Using Shamir secret sharing, one is starting with a secret and end up with a number of shares based on a polynomial. For example: INPUT: secret: 123456 Shares:4 ...
1
vote
2answers
155 views

Factoring large $N$ given oracle to find square roots modulo $N$

When $p$ and $q$ are distinct odd primes and $N = pq$, the points in $\mathbb Z_N^\ast$ have either zero or four square roots. A quarter of the points have four square roots; the rest have no square ...
1
vote
1answer
55 views

How succeptible to accidental collision is the construct sha256(uuid4 + now) in Python?

I need 32 byte pseudorandom sequences that denote unique filenames and am currently using this Python code: ...
1
vote
1answer
25 views

Question about entity authentication

Say party A wants to make sure they are communicating with party B, and not an eavesdropper E. Then they will use an authentication scheme to do this. But what if there is an eavesdropper on the line,...
1
vote
4answers
116 views

Do any cryptography algorithms work on numbers besides primes?

I know prime numbers are important for several algorithms and protocols. Are there any algorithms and protocols that don't require primes?

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