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Proxy re-encryption (PRE) is a public-key cryptography primitive that delegates the decryption capabilities of a user (called delegator) to another user (called delegatee) using a re-encryption key. A semi-trusted proxy uses the re-encryption key to transform a ciphertext under the delegator’s public key such that it becomes a ciphertext under the delegatee’s public key. If instead of “all”, a delegator wishes to delegate a subset of his decryption capabilities, there is a need for elevating the level of trust in the re-encrypting proxy. As a result, PRE in multi-proxy scenario has received significant research attention in recent times. In this paper, we introduce a new PRE primitive in a multi-proxy setting called Threshold Progressive Proxy Re-encryption (TP-PRE), that involves progressive transformation of ciphertext and results in production of a valid re-encrypted ciphertext if and only if at least t out of the total N distinct …