# Tagged Questions

In identity-based encryption (IBE) the public key of a user $A$ is some identity string $ID_A$, e.g., an email address. To encrypt a message for this user there is no need to retrieve an authentic copy of the public key, as it is in public key cryptography, but one can simply use the identity string ...

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### What is the “artificial abort” technique?

In the security proof of Brent Waters's paper Efficient Identity-Based Encryption Without Random Oracles, he uses a novel “artificial abort” step on page 6. At this point the simulator is still ...
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### How to prove identity without revealing identity

Let us say Alice publishes a book under the name of Claire. The book becomes wildly popular and now Bob comes along, claiming to be Claire, to reap all the success. How does Alice prove that she wrote ...
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### Is there any semantic difference between predicate encryption and functional encryption?

Predicate encryption(PE) arrived as a descendant of attribute based encryption. Attribute based encryption allows the encryptor to embody a policy to the ciphertext (Ciphertext-Policy based encryption)...
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### How to compare performances of lattice-based and pairing-based IBE schemes

I try to compare the performances (cost of Enc, Dec, ... size of keys, ciphertexts, ...) of IBE schemes using lattices (LWE hardness assumption) or pairing (Diffie-Hellman hardness assumption). I've ...
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### What crypto system allows for 3 parties: Party 1 who makes an assertion, Party 2 mutates the assertion, Party 3 validates it

I'm looking for the cryptographic equivalent of a Drivers license where the issuer can be verified, the issuer doesn't need to know who you showed the drivers license to, but also allows per-...
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### Generic group model: use of polynomials in the proof of the master theorem

I've been looking at the paper of Boneh, Boyen, Goh Hierarchical Identity Based Encryption with Constant Size Ciphertext which contains a general theorem (Theorem A.2) about the advantage of an ...
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### How to select corresponding ciphertext in anonymous Identity-based broadcast encryption

In identity-based broadcast encryption, suppose the broadcast ciphertext $(r_1,r_2,\dots,r_i,U,W,V)$ is sent to the receiver. It does not describe which user corresponds to which ciphertext part. User ...
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### Why is the simulation required in these identity-based encryption security proofs?

In identity-based encryption papers (i.e.this) it is very difficult for me to understand security proof. I don't know why they prove assumption (BDH, BDDH) for security of their scheme. Some uses ...
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### what is the difference between IBE and ABE schemes

Can somebody explain in simple words. real life example light help and limitations of these schemes etc.
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### a possibly stronger type of attack on identity-based encryption

What is known about the security of identity-based encryption schemes against attacks that involve seeing multiple ciphertexts and then receiving the private keys corresponding to some of those ...
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### Use of the master key in Delerablée's Identity-based Broadcast Encryption

I'm reading “Identity-Based Broadcast Encryption with Constant Size Ciphertexts and Private Keys” by Cécile Delerablée. On page 207, the encryption process needs $\gamma$ which is part of the master ...
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### Is it feasible to use combination of ABE schemes for encrypting the data?

I have a peculiar requirement for preserving the shared log files. For example I have 1000 records which belong to different organizations as listed below and all the logs are present in a single CSV ...
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### What are the benefits of being able to choose (most of) the public key in a PKC?

We're developing a public key cryptosystem whose ciphertexts are actually much more long than the plaintexts (which, according to this question, is more a benefit than an issue). However, we have a ...
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### How to run a (provably probably) secure global referendum?

The following question is extremely broad and speculative, for which I apologize, but it strikes me as exceedingly important, so I will ask it nonetheless. Suppose an event of global significance ...
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### Probability of generating same master secret key in Identity-based Encryption

Suppose multiple servers use same IBE domain parameters (I mean same curve description parameters and field) for master secret key setup. Is there any possibility for generating the same system ...
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### Advantage of attacker in CPA secure IBE

In CPA secure IBE systems, the advantage of attacker (A) is defined as absolute value of $$Pr[b=b^{'}]-\frac{1}{2}$$ Can someone please explain this to me in a few words? Where exactly does that ...
In authenticated ID-based encryption by Benn Lynn, in proof of integrity in section 4.3,Meaning of guess-ID? Why is it assumed that $L_{s}$ is empty, then $B$ fails? If guessed ID, why encryption ...