Authorized and Verifiable Searchable Encryption Based on Public Key Equality Test for Cloud Storage | Xiuping Li et al. | ResearchPod

Transcript: Authorized and Verifiable Searchable Encryption Based on Public Key Equality Test for Cloud Storage

Alex: Welcome to another episode of ResearchPod.

Sam: Today we're looking at a system called AVSE—a new approach to a genuine puzzle in cloud storage: how can you let a server search your encrypted files without giving it the power to abuse that access, or lie about what it finds?

Alex: So the core challenge is making cloud searches both secure and honest at the same time?

Sam: Exactly. Picture this: you store medical records in the cloud. You want a doctor to be able to search for "diabetes" records. But you need two guarantees. First, that the doctor can't hand that search permission to someone else. And second, that the server isn't quietly skipping files to save itself computing work.

Alex: That's like a digital boarding pass tied to your identity—you can't hand it to a friend or use it for a different flight.

Sam: That's a good way to put it. The researchers call this property "non-transferable authorization." To enforce it, they attach a unique, one-time number to every search permission—they call it a "nonce." Each search token can only be used once. If someone tries to reuse it, the system rejects it outright.

Alex: So that closes off the abuse angle. But what about the server lying? How do we actually know it searched the files properly and returned honest results?

Sam: When the server returns search results, it also has to attach a mathematical proof—a kind of receipt showing it did the work correctly. Anyone can check that receipt using information that's already public, without needing to see the actual files. The researchers call this "public verifiability."

Alex: And all of this happens without a trusted third party overseeing it?

Sam: Correct. Normally you'd need a middleman—some independent authority to certify the server behaved. This system removes that requirement entirely. The underlying tool is something called a "bilinear pairing." Think of it as a special kind of mathematical lock that can connect two encrypted values and confirm they match, without ever opening either one to see what's inside.

Alex: So it's a way to prove the server did its job honestly, using math alone, without exposing the underlying data.

Sam: Precisely. And there's another layer worth mentioning. The system doesn't just check whether two files are identical—it maps keywords to specific documents. That means whoever owns the data can set fine-grained rules: this doctor can search for "diabetes" and see these ten files, but not others. The authorization is specific, not blanket.

Alex: It sounds like they've stacked several security properties into one design. Is it actually efficient enough to use in practice, or does all that complexity slow things down?

Authorized and Verifiable Searchable Encryption Based on Public Key Equality Test for Cloud Storage

Xiuping Li, Kaiwen Wang, Xiaolin Chang

Jun 5, 2026·3:57·arxiv·Original Paper

Public Key Encryption with Equality Test (PKEET)Searchable Encryption (SE)Ciphertext-file-level AuthorizationPublic VerifiabilityPKEET (Public Key Encryption with Equality Test)AVSE (AVPKEET-based Authorized and Verifiable Searchable Encryption)

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4 min

Briefing

Research Question and Approach

Cloud storage allows users to outsource data, but searching encrypted data without revealing content remains a challenge. While Public Key Encryption with Equality Test (PKEET) allows servers to compare ciphertexts from different users without decryption, existing schemes often lack granular authorization, public verifiability, or the features required for a full-scale searchable encryption (SE) system. The authors propose a new primitive, AVPKEET, to address these gaps, and subsequently develop AVSE, a practical searchable encryption scheme built upon this primitive.

Main Findings

The authors demonstrate that AVPKEET is the first scheme to simultaneously provide ciphertext-file-level authorization and public verifiability. By binding authorization tokens to specific users, keywords, and unique nonces, the scheme ensures that tokens are non-transferable and non-replayable. The AVSE scheme extends this by adding:

Index Management: Mapping keywords to document sets for one-to-many retrieval.
Batch Operations: Efficiently handling multi-document search and verification.
Fine-grained Access Control: Providing three levels of authorization (ALL, PARTIAL, SINGLE) for document access.

Formal security analysis proves that the scheme satisfies OW-CCA2 security, token unforgeability, and verification soundness. Experimental results indicate that AVSE achieves the most compact token size (168 bytes) among comparative schemes, with performance overheads suitable for cloud deployment.

Why It Matters

This research bridges the gap between theoretical cryptographic primitives and practical cloud storage needs. By enabling public verifiability, it removes the need to blindly trust cloud providers, while the fine-grained, non-transferable authorization mechanism prevents common security pitfalls like unauthorized token sharing and replay attacks. These improvements make PKEET-based searchable encryption significantly more viable for real-world, multi-user enterprise environments.

Key Terms and Definitions

PKEET — A cryptographic technique allowing a cloud server to determine if two ciphertexts, encrypted under different public keys, contain the same plaintext.
Public Verifiability — A property allowing any user to verify the correctness of an equality test result using only public parameters, without needing secret keys or a trusted third party.
One-Time Token — An authorization credential bound to a specific user, keyword, and nonce, ensuring it cannot be reused or transferred to unauthorized parties.
OW-CCA2 — A security model (One-Wayness against Adaptive Chosen Ciphertext Attack) ensuring that an adversary cannot recover the plaintext or gain information even with access to a decryption oracle.
Forward Security — A property ensuring that if a token is compromised, it cannot be used to access data uploaded to the system after the token was issued.

Abstract

Cloud storage revolutionizes data management but raises conflicts between functionality and privacy. Public Key Encryption with Equality Test (PKEET), an advanced cryptographic technique, can enable multi-user searchable encryption (SE) through cross-key ciphertext comparison without shared keys. However, existing PKEET-based SE schemes lack ciphertext-file-level authorization, public verifiability, or SE-level support. This paper first proposes a novel PKEET scheme, AVPKEET (Authorized and Verifiable PKEET). It enables non-transferable and non-replayable authorization of ciphertext files, while supporting public verifiability, all without the need for trusted third parties. Then we propose an AVPKEET-based SE scheme, denoted as AVSE (Authorized and Verifiable SE), featuring one-time non-transferable tokens bound to users and nonces, batch operations, and fine-grained access control (ALL, PARTIAL, SINGLE). We prove OW-CCA2 security, token unforgeability, and verification soundness under standard assumptions. Experiment results demonstrate that AVSE achieves the most compact token size (168 bytes) while uniquely providing both ciphertext-file-level authorization and public verification, with acceptable overhead for cloud storage deployment.

Authorized and Verifiable Searchable Encryption Based on Public Key Equality Test for Cloud Storage: Research Paper Podcast