# All Questions

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### 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?

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 ...
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### How to force an adversary to call a certain oracle?

Consider there is a protocol in real world, which uses a random oracle $\mathcal{H}$. In the ideal world, after the calling of $\mathcal{H}$ by some parties, intuitively I want the simulator gets some ...
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### StoredKey in Salted Challenge Response Mechanism (SCRAM)

In SCRAM (RFC5802, page 8) the client generates ClientKey to server, which is a derivation of the original password. This is communicated to the server in a secure ...
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### User revocation in Identity Based Encryption

I read several papers about user revocation in IBE recently. A common point is that when a user is revoked, some other valid users should also update their private keys. Does this mean that one ...
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### Deletion in RSA Accumulator

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 ...
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### David Chaum's anonymous credential

I am a newbie in cryptography (I know the basic RSA, AES stuffs) and am interested in anonymous authentication systems. Looks like David Chaum is the godly figure in the field. I see lots of people ...
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### What's the perfect chain length : number of chains ratio for rainbow tables?

I'm building a SHA-1 rainbow table to crack basic passwords (i.e. up to 10 character, 0-9,a-z). But I can't seem to calculate that golden ratio that would give me the most coverage. Also is there ...
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### Multiple levels of encryption

Is it feasible to have data encrypted at different levels of hierarchy I'd like to encrypt an xml database (such as used in www.keepass.info) whereby two or more keys can exist. For example: Key #1 ...
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### Reference AES-NI assembler code for AES-128-GCM? [closed]

I want to implement AES-128-GCM in assembler using Intel AES-NI instructions. I have found reference code in the Intel AES-NI Whitepaper but I don't see code for the GCM mode there (or indeed any use ...
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### Upper bound on r* on page 7 in the Scale Invariant Fully Homomorphic Encryption over the Integers paper

I was hoping to get some clarification on how the bound on r* was calculated (bottom of page #7). I'm trying to reproduce the results that have been shown, however I keep getting a slightly smaller ...
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### Are there any real-world E-voting systems in use with the Paillier cryptosystem?

There are a lot of theories of Paillier cryptosystem with references to e-voting. Are there any real-world E-voting systems in use with the Paillier cryptosystem?
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### Are there any FHE-MPC schemes implemented?

I want to know if there are any publicly available multiparty computation schemes derived from fully homomorphic encryption schemes. An example would be the implementation of this scheme https://...
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### If a PRG is constructed by iterating a PRF, is it backtracking-resistant?

Say we construct a pseudo-random number generator from a pseudo-random function $f$ (using some constant key $k$ and some initial value $v_0$). We do this by feeding the output block of the PRF back ...
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### PathORAM with read path eviction

I am currently trying to implement the pathORAM algorithm as describe in this paper: https://eprint.iacr.org/2013/280.pdf The paper states that with high probability, the stash size will be bounded ...
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### Why is SSL/TLS so complicated?

I'm new to SSL/TLS and I'm staring as a new security researcher. It appears to me that SSL/TLS protocol is needlessly complex for arriving at a shared secret. The complexity results in so many bugs (e....
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### Find plaintext from two ciphers encrypted with a one-time pad and the same key

I'm studying for a cryptography test and I came across this question: Assume a language has three letters: A=1111, B=0011 and C=1010. Two words in this language are encrypted with a one-time pad ...
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### How does Intel TXT prevent spoofing of PCR values?

I have read some content on trusted execution environment, and I like to ask exactly how it improves hashing. What I read at Wikipedia’s “Trusted Execution Technology” article states: ...PCRs) ...
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### Raw /dev/random output for keymat [duplicate]

Noob question: It is my understanding that the raw output from non-blocking /dev/random (where the kernel's entropy_avail estimate is equal to or greater than the number of random bits required) ...
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### Using a product of a series of curve25519 scalars as a private key

There are a few systems like the GNU Name System and the Sphinx mixnet packet format that employ a series of curve25519 scalars all multiplied together as a private key. Are there any caveats to ...
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### Detecting steganography by analysing non-significant data entropy?

I am not thinking only steganography in images, I think it is also possible to encode data for example into the length of spaces of a clear html text. I suspect, the steganography changes (elevates) ...
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### How does FileVault2 Recovery actually work?

I'm a crypto-enthusiast but no expert at all, that'll explain why i didn't understand. Also please consider english isn't my native language :) I am about to enable FileVault2 FDE on the new macbook ...
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### Most Secure Exchange of Keys [closed]

Given both Alice and Bob must exchange IP addresses to perform such an operation, what is the most secure way Alice and Bob can exchange public keys between two mobile devices without having to rely ...
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### Test vectors for TLS PRF function

Does anyone know where I might be able to find test vectors for the PRF function in TLS? (either 1.0 or newer). I'm trying to implement a client and I am getting the BAD Record MAC return after ...