  A pseudonymisation technique based on Merkle trees is described in this
paper. More precisely, by exploiting inherent properties of the Merkle trees as
cryptographic accumulators, we illustrate how user-generated pseudonyms can be
constructed, without the need of a third party. Each such pseudonym, which
depends on several user's identifiers, suffices to hide these original
identifiers, whilst the unlinkability property between any two different
pseudonyms for the same user is retained; at the same time, this
pseudonymisation scheme allows the pseudonym owner to easily prove that she
owns a pseudonym within a specific context, without revealing information on
her original identifiers. Compared to other user-generated pseudonymisation
techniques which utilize public key encryption algorithms, the new approach
inherits the security properties of a Merkle tree, thus achieving post-quantum
security.
