In public key crypto, can there be one single public key and multiple private keys?
Thursday, October 15th, 2009 at
10:53
I have a message that I want to distribute to multiple people, but I only want to make one copy of the same encrypted message. In that case, I want to encrypt the content with a single public key, but each of the recipients has to use his/her unique private key to decrypt.
Is such a single-public-key/multiple-private-keys relationship possible?
Tagged with: decrypt • encrypted message • private key • private keys • public key • relationship
Filed under: crypto and decrypt
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Not possible. But the following techniques will solve your problem:
1) Use secret Shamir sharing schemes : Where you can share the private key into n number of parts. And any t<n number of users can combinely read the message. But it will require at least more than 2 key holder to read the message.
2) Use multiple private key and multiple public key.
No. All intended recipients will need the same private key.
I see you’re talking about Asymmetric Cryptography. This is where both private and public keys differ. To ensure that the message is encrypted and can be decrypted by intended parties, you can encrypt your message with your own private key, then distribute your public key to those that you want to view the message.
That’s because only people with your public key can decrypt your message encrypted by your private key. You’re doing things the other way round, there’s no such thing as multiple private keys.
Private key works like a lock, you only give your keys (Public key) to those you want to be able to unlock it.
However there’s another stronger type of encryption, which utilizes both symmetric and asymmetric cryptography. You encrypt the message using symmetric encryption, then encrypt the symmetric key with your private key. This is known as a digital signature. Then, just send the encrypted key and contents to intended recipents and they’d be able to use your private key to decrypt your key and use the key to decrypt your message.
Hope this helps…