# All Questions

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### How to attack CBC and OFB by knowning plaint-text and its cipher-text?

In the CBC and OFB encryption with fixe IV and by knowing the plaint-text and its cipher-text how we can decrypt the other cipher-texts? Thank you
22 views

### Is it secure to use ECDSA for any arbitrary point on the Elliptic Curve as the Generator point?

My question concerns the elliptic curve $E$ over a prime field $\mathbb F_p$. To the best of my understanding, ECDSA requires a Generator point $G$ of prime order $n$, and the $r$ and $s$ values of ...
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### Implementation of designated verifier signature success sometime and fail sometime [migrated]

I am trying to implement JSO Designated Verifier Scheme by Java. I follow the paper above to implement it. But I get a very strange result, which sometime the verification is success and sometime fail....
129 views

### For Diffie-Helman, why is a g value of p − 1 not a suitable choice?

I am currently learning about the Diffie-Helman key exchange. I understand that for a $g$ of $1$, you're resulting key would always end up as one which would obviously not be secure. However, I read ...
37 views

### Finding out cryptography method used and decrypting it [closed]

I used Frida to do an MITM attack on an android app and I was able to successfully record network transmissions but there was one problem, all the requests sent to server was encrypted. Then i tried ...
46 views

### Licensing software with asymmetric signed files

NOTE: I know that there are numerous topics here on StackExchange about this but I've read them all and this question still persists. I'm currently working to enhance the security of a windows based ...
25 views

### Cracking a Shift Cipher that uses an Unknown Deterministic Scheduling Algorithm

Consider a shift cipher that has the following encryption scheme: The plaintext contains lowercase characters and spaces, is composed of English text, and is about length 500. Thus, the message (and ...
14 views

### Decrypting data on client side for use inside program

So I am developing a python program and encrypting the trained machine learning models which need to be decrypted when loading them on client side. My program will deployed on the client's machine ...
48 views

As the Logjam attack allows a man-in-the-middle attacker to downgrade vulnerable TLS connections to 512-bit export-grade cryptography by modifying the ClientHello and ServerHello. Can the Logjam ...
24 views

64 views

### Using SHA384 as an asymmetric cipher?

SHA384 is a hash function that can be (and is) used to verify data by checking it. Can it also be used as the background for a public-key crypto system? Here is what I mean: A 48-byte string is ...
82 views

### How to Sample from Frobenius Eigenspace?

So I was implementing the $2$-point method described here[1], which requires to samples two points $P_0, P_1$ in the Frobenius eigenspace initially. It uses a method called Elligator, which seems to ...
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### libgcrypt and rdrand usage

for some reasons, i was looking into libgcrypt source code and found this : https://github.com/gpg/libgcrypt/blob/b64b029318e7d0b66123015146614118f466a7a9/random/rndlinux.c#L189 if i understand this ...
61 views

### How can I prove a truncated hash fuction need not be collision resistant?

Let $H : \{0, 1\}^∗ \mapsto \{0, 1\}^ n$ be a collision-resistant hash function. Define $H_0(M) = H(M)\mathbin\|0^{n−10}$. That is, $H_0$ appends ($n − 10$) zeros to the output of $H$. Clearly $H_0$ ...
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### Relation between LPN and GAPSVP?

I have a question regarding the relationship between the (search) LPN problem and the GapSVP problem. I have read a related problem that explains the main theorem in Reg05: the GapSVP problem can be ...
30 views

### Decryption in Goldwasser-Micali Scheme

Referring to the following URL: http://cryptowiki.net/index.php?title=Goldwasser_Micali_cryptosystem The decryption of the message is based on wether the bit is a QRn or not, but how do we know/...
86 views

### Finding the IV values of SHA-256 given all message blocks

Given all message blocks $w[i],i \in 0:63$ and assume that $n<128$ (arbitrary) bits $x_1,x_2,...,x_n$ of the IV values are unknown (e.g., $h_7$ bits are unknown) while other IV values coincide with ...