In light of recent research into the security of end-to-end encrypted cloud storage systems, it’s becoming increasingly clear that while many services claim to offer privacy, few can truly deliver on that promise. A recent paper, End-to-End Encrypted Cloud Storage in the Wild: A Broken Ecosystem (source), analyzed five major E2EE cloud storage providers and found numerous vulnerabilities.
These findings underscore the critical flaws in the cryptographic implementations used by many cloud providers. However, one platform stands apart from these—Züs’s Vult and Blimp. While Züs was not part of the study, we are confident that its unique approach to encryption makes it a far more secure option. As Saswata Basu, Cofounder of Züs, explains:
“Recent research cited in this article highlights significant vulnerabilities in end-to-end encrypted (E2EE) storage solutions, primarily due to server-generated keys that lack user identities. Zus addresses this issue by anchoring user identities on the blockchain, with all encryption keys (session or re-encryption) derived from this identity. This approach makes Zus an ideal storage solution for safeguarding data and maintaining privacy.”
Security is built into the core of our architecture, ensuring that your data and keys remain safe—and under your control. We are proud to say that the weaknesses identified in the research simply do not apply to Züs. Here’s why:
1. Unauthenticated Key Material
The Problem: Sync and pCloud fail to authenticate key material, allowing attackers to inject malicious keys.
Züs Solution: All encryption keys are securely generated on the client side. Blobbers (storage providers) have zero access. Our re-encryption process, powered by BLS-based master wallet keys, ensures injected or tampered key material is cryptographically impossible.
2. Unauthenticated Public Keys
The Problem: Sync and Tresorit use unauthenticated public keys, vulnerable to server-based attacks.
Züs Solution: Public keys in Züs are authenticated and derived directly from master wallet keys, ensuring origin integrity and preventing unauthorized data access.
3. Protocol Downgrade Attacks
The Problem: Seafile allows attackers to force a downgrade, exposing weaker protocols.
Züs Solution: All protocol transitions on Züs require user authentication. Downgrade attacks are structurally impossible.
4. Link-Sharing Pitfalls
The Problem: Sync embeds passwords in share links—easily intercepted or guessed.
Züs Solution: Züs personalizes encryption for the recipient. Only the intended user can decrypt the file, eliminating any risk from link sharing.
5. Unauthenticated Encryption Modes
The Problem: Icedrive and Seafile use cipher modes like CBC without authentication, enabling tampering.
Züs Solution: Züs uses authenticated encryption schemes that ensure confidentiality and file integrity.
6. Unauthenticated Chunkin
The Problem: Seafile and pCloud allow file tampering by modifying or replacing data chunks.
Züs Solution: All chunks are integrity-verified using ranged Merkle trees, with user-signed roots—ensuring tamper-proof files.
7. Tampering with File Names and Locations
The Problem: Most systems don’t bind file names or locations cryptographically, allowing manipulation.
Züs Solution: Every file upload is signed by the user, making it impossible to spoof or alter file names or storage locations.
8. Tampering with File Metadata
The Problem: Metadata like file size or type can be altered undetected.
Züs Solution: All metadata in Züs is cryptographically authenticated and signed, ensuring accurate file descriptors.
9. Injection of Folders and Files
The Problem: Sync and pCloud allow server-side injection of content.
Züs Solution: Every file and folder operation is authenticated and validated via Merkle trees and user signatures, blocking unauthorized injections.
10. Encryption Key Management Vulnerabilities
The Problem: Mega exposes keys to the server (as ciphertext), risking exposure in man-in-the-middle or server breach scenarios.
Züs Solution: Encryption keys in Züs are never stored server-side. They are generated client-side and used only transiently. Even the re-encryption key—used by the 0box microservice—is securely shared and isolated per transaction.
A Call to the Authors: Test Vult and Blimp for True Security
If the findings in the ETH paper are correct, then our storage platform is a game-changing feature for cloud storage security. No one else offers this level of protection, and we believe it’s crucial for researchers, developers, and security professionals to consider Züs as the gold standard in secure cloud storage.
To further understand the cutting-edge cryptographic approaches Züs utilizes, we invite you to explore the following papers, which demonstrate the power of proxy re-encryption and key splitting—core principles integral to Züs’s platform:
Sharing of Encrypted Files in Blockchain Made Simpler
By: S. Sharmila Deva Selvi, Arinjita Paul, Siva Dirisala, Saswata Basu, C. Pandu Rangan
This paper introduces Proxy Self Re-encryption (SE-PRE), a highly efficient cryptographic technique designed for secure file sharing in blockchain-enabled distributed cloud storage. SE-PRE simplifies the process of re-encrypting ciphertexts towards legitimate users via semi-trusted proxies without compromising security or efficiency.
Splitting and Aggregating Signatures in Cryptocurrency Protocols
By: S. Sharmila Deva Selvi, Arinjita Paul, C. Pandu Rangan, Siva Dirisala, Saswata Basu
This work explores the cryptographic efficiency of key splitting and aggregation techniques, which are crucial for improving scalability in blockchain and cryptocurrency protocols. The paper proposes using the BLS short signature scheme, which excels at both key splitting and aggregation, offering enhanced computational efficiency.
About Züs
Züs is a zero-trust, ACID-compliant, blockchain-secure storage platform engineered to be breachproof. It offers unlimited scalability, encrypted data sharing, full data ownership, and unified data visualization—supporting use cases from datalakes and lakehouses to backup and disaster recovery. The master key is anchored on the blockchain and secured within an enclave, while operational split-keys provide an additional layer of protection. Data is distributed across multiple servers to safeguard against breaches, hacks, and ransomware. The client-server relationship is established on-chain, and all data exchanges are validated through authenticated messages and Merkle tree proofs, ensuring both security and integrity.
Website: https://zus.network/
Enterprise Storage: https://www.blimp.software/
Private Drive: https://www.vult.network/
Contact Information
If you are part of the research team or wish to discuss Züs’s security further, we would love to hear from you at store@zus.network.
