Certificateless cryptography
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Certificateless cryptography is a variant of ID-based cryptography intended to prevent any need for key escrow. It does this by splitting the private key generations stage between a user and a third party. One disadvantade of this is that the identity information no longer forms the entire public key.
To encrypt a message to another user, three pieces of information are needed: 1) the other user's public key and 2) identity, and also 3) the third party's public information. To decrypt, a user just needs to use their private key.
This system doesn't need certificates as no valid pair of private & public key can be generated without the secret information provided by the third party.
Although the level of trust that is placed in the third party is reduced in this system it is still high, as high as that placed in certificate authorities. This is because if the third party wished to break the system by generating fake public keys, it could still do so. It could not however decrypt messages which have been encrypted using a properly generated public key.