Secrecy through Synchronization Errors

In this paper, we propose a secure transmission scheme based on deleting and inserting symbols. The proposed encryption/decryption method is novel since it achieves secrecy by a transmitter that deliberately introduces synchronization errors (insertions and/or deletions) based on a shared source of randomness. The intended receiver, having access to the same shared source of randomness as the transmitter, can resynchronize the received sequence. On the other hand, the eavesdropper´s channel remains a synchronization error channel. We show that the scheme achieves information theoretic security. We prove a secrecy capacity theorem, provide a lower bound on the secrecy capacity, and propose numerical methods to evaluate it.