FlagThis

Abstract

We present Safecloud, a distributed, encrypted, self-pricing storage and streaming network in which the nodes that provide storage never observe plaintext and never hold decryption keys. Safecloud splits each file into fixed-size chunks, encrypts every chunk on the owners device before it leaves, and distributes the resulting ciphertext across two classes of node: Drops, which run inside ordinary web browser tabs and store encrypted chunks in IndexedDB, and Jets, federated routing servers that match chunks to Drops and serve retrieval requests. Only the Cloud the file owner or an authorised grantee ever holds keys. We make five contributions. First, a one-root key hierarchy: every key in the system is derived deterministically from a single root secret by HKDF with domain-separated labels, so that nothing but the root need ever be stored, and we prove that chunk keys derived by an owner and by a range-scoped grantee coincide (derivation agreement). Second, convergent content addressing: because derivation is deterministic, identical content under the same root yields identical ciphertext and hence identical content identifiers, enabling deduplication without exposing plaintext, and we show the content identifier binds the authenticated ciphertext so that a Drop can verify it holds the correct chunk with no key (blind verifiability). Third, three parallel trees over one navigation path a public Merkle tree for integrity, a top-down key-derivation tree for confidentiality, and an access tree for authorisation so that one link path simultaneously locates a chunks integrity proof, its decryption key, and its access grant, and we prove Merkle-verified retrieval detects any substituted or corrupted chunk (retrieval soundness). Fourth, the top-down key tree doubles as a streaming structure: a player derives each successive segment key in O(1) from a node it already holds, so seeking is a derivation rather than a re-traversal, a files parallel tracks (video, audio, captions) are independent subtrees unlockable separately, and access can be scoped to a segment range within a track—a combination of random-access decryptable streaming and per-track, per-segment monetisation we believe no prior encrypted-storage network offers. Fifth, Jets and Drops earn Safebux verifiably for routing and storage, settled through OpenClaiming trustlines and kept honest by a one-signature proof-of-storage challenge under the chilling-effect Proof-of-Corruption discipline of Intercloud [1]—a zero-sum economy we argue is structurally cheaper than Filecoins proof-of-replication sealing that does not itself provide confidentiality [5], [6]. Safecloud composes with the attested execution of Safebox [2] where confidential server-side custody is required, and uniquely places both supply and demand inside browser sessions: a visitor leaving a tab open becomes a storage provider with no installation. We describe the architecture, the cryptographic construction, a threat model, and an open-source reference implementation, and we state precisely which components are implemented and which are designed and in progress. Safecloud 2.0 [3] extends the same substrate from verifiable storage to verifiable computation.