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.