Questions tagged [identity-based-encryption]

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 $ID_A$.

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Is it possible to verify attributes of encrypted content?

Let's say that Alice has this information about her, { "name": "Alice", "age": 25, "eyes": "brown" } which she encrypts with a key pair so that no one access ...
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New Pairing Friendly Curves for SM9

A paper was presented at the INSCRYPT 2018 called: "Searching BN Curves for SM9" http://xxhb.fjnu.edu.cn/_upload/tpl/06/5d/1629/template1629/papers/88.pdf SM9 is a Chinese National Identity Based ...
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About Cocks IBE

Why doesn't Cocks IBE use the hash function H from ID space to quadratic residue set $\mathbb{QR}_N$ in $\mathbb{Z}/N\mathbb{Z}$ to reduce the ciphertext expansion by half? I think it is also IND-ID-...
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RIBE Scheme Implementation - How to encrypt message

This question is regarding "A Fully Secure Revocable ID-Based Encryption in the Standard Model" - Tung-Tso TSAI, Yuh-Min TSENG, Tsu-Yang WU The encryption method specifies part of the encryption ...
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Problem in generation of keys in KP-ABE

In KP-ABE the owner encrypts the message using attributes say a'. The Attribute authority(AA) designs an access structure and implants that access structure in keys generated by AA for the user. So, ...
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Can I replace DH by a post-quantum key exchange in IBAKE for post-quantum identity-based authenticated key exchange?

IETF RFC 6539 IBAKE - Identity Based Authenticated Key Exchange describes a Hybrid key exchange using both Identity based cryptography and a standard ephemeral elliptic curve Diffie-Hellman key ...
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Is Identity-based encryption used in the wild?

I have a curious question. Is Identity-based encryption used in the wild?
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Can anyone elaborate why KP-ABE is better than CP-ABE for television program broadcasting?

I know the difference between KP-ABE and CP-ABE. I am not able to understand why KP-ABE is better for broadcasting than CP-ABE ?
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Difference between Identity-based encryption and multiple key-pairs of public key encryption?

What is the difference between Identity-based encryption and multiple key-pairs of public key encryption scheme?? Suppose trusted key generator generates a bunch of public and private key pairs $(k_{\...
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identity based encryption-Private key [duplicate]

PKG will be sending the Private key,so it may not be secure,some one may get the private key,how to overcome this problem in IBE. Please help am unable to justify.
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The semantic security in Anonymous Hierarchical identity-bases encryption?

In Anonymous Hierarchical Identity-Based Encryption (Without Random Oracles) by Boyen, to prove security it defined challenge ciphertext like I actually can't get how does the proof work? Why we ...
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How to ask for an Identity confirmation without revealing

Let us say Alice has a list of public keys of her contacts. Bob wants to contact Ted and Bob has public key of Ted. Now, Is it possible to confirm that Alice has the same public key, without ...
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How can I implement ID based encryption using RSA?

I want to implement ID based encryption using the RSA encryption algorithm but how can I edit the algorithm for IDs.
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Enabling Oblivious Access Control via Function Encryption

Abstract With Functional Encryption, would access control between two parties be possible without revealing the entirety of one party's policy to the other? E.g. such that a server would be incapable ...
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Bilinear Form: Weil pairing

I am doing an example on Weil pairings, and for that purpose I follow the thesis of Alex Edward Aftuck, The Weil Pairing on Elliptic Curves and Its Cryptographic Applications. By following his thesis,...
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Are pairings still the most efficient implementation for identity and attribute-based encryption?

I read on Wikipedia: [...] pairings have also been used to construct many cryptographic systems for which no other efficient implementation is known, such as identity based encryption or attribute ...
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identity based cryptography (IBE) without key escrow

I am trying to find a method of implementing identity based cryptography to generate key pairs without the use of a trusted PKG that holds the private keys. Has there been any solutions to overcoming ...
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Are Koblitz curves paring friendly?

I want to implement an identity based encryption scheme using Koblitz curves as scalar multiplication is faster due to Frobrenius endomorphism. How can I tell if a curve over $\operatorname{GF}(2^m)$ ...
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Proof of a key agreement protocol based on bilinear pairings

I'm currently trying to understand a proof of a protocol of the paper of Liqun Chen and Caroline Kudla entitled "Identity Based Authenticated Key Agreement Protocols from Pairings". You can find a ...
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Security of the server's private key

In some papers, server generates keys for users as follows: $$sk_i=msk+H(ID_i)v_i\ (mod \ p)$$ where $msk=$ the secret key of server $v_i$ is randomly selected from $Z_p$ for i-th user , $p$ is a ...
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How are private keys handed to users in Identity-based Encryption?

I'm using IBE in my applied-crypto project in primitive form. I saw many articles about IBE, but didn't find how user can get private key is generated by PKG after EXTRACT method. So, my question: ...
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Why use symmetric encryption in a protocol like UPORT?

Reading the whitepaper UPORT: A PLATFORM FOR SELF-SOVEREIGN IDENTITY ~ DRAFT VERSION (2016-10-20) I noticed it states : Let A be an attestation. Suppose we wish to share this attestation with ...
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Computational Assumption For the extended discrete logarithm

Choose randomly $P\in G_1, (s,a \in Z_q)$. let the attackers know $a,P$ and keep $s$ as secret. Also the following is given. $$sP,(a+s)^{-1}P$$ Individually, From $sP$, trying to reveal ($s$) will ...
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Can I use computational diffie hellman problem in the following scheme?

Suppose $$X=mnrP , Y=\frac{1}{n}Q, R=e(P,Q)^m$$ $X,Y,P,Q$ are randomly chosen from $G_1$.And only $X,Y$ is given in public. $m,n,r$ are randomly chosen from $Z_q$. Anybody who knows $(1/r)$ can ...
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Selecting secret value in certificateless identity-based encryption

In certificateless identity-based cryptography, selecting secret value $$x_i \in Z_p$$ and declaring public key of individual users such as $$Pub_i=g^{x_i}$$ $g$ is public parameter. I think there ...
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Anonymous Multi-Receiver Identity-Based Authenticated Encryption with CCA Security?

OK, I am confused. Does it mean that that the various anonymous multi-receiver IBE implementations actually do not have single public key per Identity, as as is the in the original IBE implementation? ...
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How to distribute system parameters in identity-based encryption

Identity-based encryption papers describe that system parameters are declared as public. However,in real scenario, how to distribute system parameters to users?
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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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Some Question about Security Proof of authenticated identity-based encryption

In authenticated identity-based encryption by Benn Lynn, in proof of security, I have a little difficulties in understanding. In key extraction queries,if attacker request for guessed ID, then B fails....
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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 ...
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Why security proof uses random oracles in identity-based encryption?

In identity-based encryption, users decrypt the ciphertext by using private keys. Without private key, no one will be able to decrypt.In security proofs like here, random oracles are used with the ...
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Decryption Queries and its meaning in identity-based encryption

In identity-based encryption, for security proof, they sometimes describe random oracle for decryption queries. Therefore, I wonder decryption is handled by decryption oracle for all users? Users need ...
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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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Why not consider modification in ciphertext part in identity-based encryption

In identity-based broadcast encryption system, the ciphertext is $$ C=<c1,c2,...,cn,U,V,W>$$ There can be a man-in-the-middle who can modify one or all of the $c1,c2,...,cn$ values so that the ...
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Anonymous Identity-based broadcast encryption use single common key or different keys

In identity-based broadcast encryption, suppose the broadcast ciphertext $(r_1,r_2,\dots,r_i,U,W,V)$ is sent to the receiver. In some cases, they use some function $f(x)=k-\prod_{i=1}^{t} (x-v_{i})$ ...
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Notation of * in hash function of identity-based encryption

$H:\{0,1\}^{*} \rightarrow Z_{p}^{*}$ $H:\{0,1\}^{*} \rightarrow Z_{p}$ $H:\{0,1\}^{*} \rightarrow G_{1}^{*}$ $H:\{0,1\}^{*} \rightarrow G_{1}$ Difference meaning of $Z_{p}^{*}, Z_{p},G_{1}^{...
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Hash Function representation in identity-based encryption

Some describe as $H:F_{q}\times G_{2}\rightarrow \{0,1\}^{n}$.Some describe as $H:\{0,1\}^{*}\times\{0,1\}^{*}\rightarrow F_{q}$. What is the meaning of product function? what kind of operation does ...
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Security (CPA?,CCA?) in Authenticated identity-based encryption

When I read authenticated identity-based encryption by Ben Lynn, encryption works to send data from user A to user B where: $$a=e(d_{A},B)$$ $$s=H_{3}(Msg,K)$$ $$C=<s,\gamma \oplus H_{2}(a,s),H_{4(...
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Which one is correct probability formula for the same master secret value in identity-based encryption

Assume two servers $(n=2)$ use the same domain curve parameters and same hash function $H:\{0,1\}^{*} \rightarrow G_{1}$ . Then the hash value for the same identity falls in same result and let it be ...
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Concept of “guessed ID” in Authenticated Identity-Based Encryption

In Authenticated Identity-Based Encryption by Ben Lynn, in Proof of Integrity (section 4.3) and Proof of Security (section 4.4), I cannot grab the concept of "guessed ID" . Because encryption differs ...
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Which one has better Performance?

Sending secret value in identity-based encryption Using xor : $K \oplus e(g,h)^{\gamma}$ Using symmetric key: Assuming $Key=e(g,h)^{\gamma}$ and encrypt $K$ using $Key$. Which one is better in ...
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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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Boneh/Franklin Identity based encryption with Tate pairing

Boneh/Franklin developed an identity based encryption scheme based on the Weil Pairing. This algorithm has also been standardised in IEEE P1363.3 . I know that this algorithm can also be implemented ...
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Possibility for same Private Key Generation in identity-based encryption

In private key generation of IBE scheme, private key is generated as follows: $SK_{ID}=s.H(ID)$ Suppose two servers use the same curve domain parameters. If PKG on server A generates private key $SK_{...
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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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Subscript R notation for the finite fields

I'm trying to understand the notation used in the literature for Pairing-based cryptography. I know (and I hope I've understood it well) from Wikipedia that $\mathbb{Z}_p$ is the finite field of ...
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Is the Discrete logarithm problem suitable for this pairing scheme?

Let $Ans$ be the product of two pairings : $e(g,h)^{k} \times e(g,h)^{r}=Ans$ If everybody knows only $[g,h,e(g,h)^{k}]$ but $[r,Ans]$ is not known. In the discrete logarithm problem, the user knows ...
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How should I define order according to domain parameters in elliptic curve pairing groups?

According to domain parameters, as an example Type 1 pairing domain parameters are ...
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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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Identity-based proxy re-encryption using different system parameters

I am wondering if there is an identity based proxy re-encryption scheme (such as the Green-Ateniese scheme https://eprint.iacr.org/2006/473.pdf) that converts an encryption computed with ID1, system ...