Abstract (EN)

Encryption key safety is the Achilles’ heel of cryptography. Backup copies with the escrow offset the risk of key loss, but increase the danger of disclosure. We propose Recoverable Encryption (RE) schemes which alleviate the dilemma. The backup is encrypted so that the recovery is possible in prac-tice only over a large cloud. A 10K-node cloud may recover a key in at most 10 minutes, with the 5 minutes average. Same attempt at the escrow’s site, a com-puter or perhaps a cluster, could require 70 days with the 35 days average. Large clouds are now affordable. Their illegal use is unlikely. We show feasi-bility of two schemes with their application potential.