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In identity based encryption, there is a key generator that gives out secret keys, and a master public key that the sender needs for encryption. To encrypt a m

In identity based encryption, there is a key generator that gives out secret keys, and a master public key that the sender needs for encryption. To encrypt a message, the master public key and the receiver's "identity" (e.g. email address) are used. Thus the sender and the receiver do not need to exchange keys in advance; the receiver must get their decryption key from the key generator, but there is no need to do so before the message was actually encrypted. The key generator can decrypt any message, of course. That is why I said threshold systems should be used, so that no single party is the key generator. In that model, the receiver would have to request that several parties jointly compute and issue the decryption key. It is also reasonable to imagine a world where there are many IBE authorities, and the sender of the message can choose which IBE authority the receiver will have to get their keys from. https://en.wikipedia.org/wiki/Identity_based_encryption https://en.wikipedia.org/wiki/Identity_based_encryption

Retric 14y ago
Think it through, your treating public information as a private key which is hardly secure. You could also use the users email address as the seed for a random number generator which would spit out keys and not involve 3rd party's but that's also unsafe. After all, what tells the Key Generator that bob@bob.com is actually bob@bob.com and not Alice?
- betterunix 14y ago
  I think you should actually read the Wikipedia IBE article, it basically answers your questions.
  - Retric 14y ago
    I did. Look at the picture provided it's the authenticate step that's the problem. Alice wants to send Bob a message. Alice contacts public key authority and says give me bob@bob.com's private key, encrypts the message and sends it. So far so good. Now, someone contacts the key authority and says I am Bob@Bob.com what's my private key. Without prior communication between Bob and the key authority there is no way to do that exchange over an open channel securely. Assuming email addresses are public information and someone can get bob's email address before he communicates with the key authority.
    - Retric 14y ago
      Err, I did. Look at the picture provided it's the authenticate step that's the problem. Alice wants to send Bob a message. Alice contacts public key authority and says give me bob@bob.com's public key, encrypts the message and sends it. So far so good.

Retric 14y ago

Think it through, your treating public information as a private key which is hardly secure. You could also use the users email address as the seed for a random number generator which would spit out keys and not involve 3rd party's but that's also unsafe. After all, what tells the Key Generator that bob@bob.com is actually bob@bob.com and not Alice?

betterunix 14y ago
I think you should actually read the Wikipedia IBE article, it basically answers your questions.
- Retric 14y ago
  I did. Look at the picture provided it's the authenticate step that's the problem. Alice wants to send Bob a message. Alice contacts public key authority and says give me bob@bob.com's private key, encrypts the message and sends it. So far so good. Now, someone contacts the key authority and says I am Bob@Bob.com what's my private key. Without prior communication between Bob and the key authority there is no way to do that exchange over an open channel securely. Assuming email addresses are public information and someone can get bob's email address before he communicates with the key authority.
  - Retric 14y ago
    Err, I did. Look at the picture provided it's the authenticate step that's the problem. Alice wants to send Bob a message. Alice contacts public key authority and says give me bob@bob.com's public key, encrypts the message and sends it. So far so good.