I know the difference between KP-ABE and CP-ABE. I am not able to understand why KP-ABE is better for broadcasting than CP-ABE ?
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1$\begingroup$ crypto.stackexchange.com/q/18123/7431 - from one of the comments - CP-ABE processes the full access tree during encryption, KP-ABE only does it during key generation $\endgroup$– NatanaelMar 10, 2019 at 23:04
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Moderator note: the next section in this answer is an edit, made by Ernesto Gómez, of the original, accepted answer. That edit also reversed CP-ABE and KP-ABE in the last section.
The question is badly elaborated:
Normally people don't elaborate that KP-ABE is better than CP-ABE,
Normally people do elaborate that KP-ABE is worse than CP-ABE,
In Ciphertext-Policy Attribute-Based Encryption the policy is in the Ciphertext. In Key-Policy attribute based encryption the policy is in the decryption key.
After this clarification, Why CP-ABE is "better" than KP-ABE?
Let's say if we want to encrypt a cartoon musical movie, and it can be watched by children users:
In CP-ABE, we can encrypt the movie with attribute cartoon and musical, and then generate a secret key with attribute structure cartoon AND musical for children users.
In KP-ABE, we have to think in the way that only users attributed with cartoon AND musical can decrypt, and then generate the secret key with attribute cartoon and musical for children users.
Although both encryption works, CP-ABE is more intuitive for broadcasters, because we only need to encrypt the movie with its types during production. Besides, it is also more flexible because we can add new users with personalized types without re-encrypting the video.
