Let‘s assume there are two keypairs
d2 are unrelated private keys and
e2 the corresponding public keys. Imagine Alice knowing neither
e2 and Bob only
e2. Alice has a ciphertext
c resulting from encrypting a message
d1 using RSA. She cannot decrypt it because she doesn‘t know
e1. Alice encrypts
c again with
d2 using an asymmetric cipher (remains to be chosen) and sends it to Bob. Bob can‘t decrypt it since he doesn‘t have
e2. Can he then use some kind of algorithm and
e1 to produce something which he can send to me that can be decrypted with
e2 resulting in the original message?
What I want is, that Alice and Bob cannot read the message, only their combined knowledge would allow them to decipher it.
m is the message
c := RSAEncrypt(m, using: d1)
c2 := AsymEncrypt(c, using: d2)
c3 := RSADecryptAlgo(c2, using: e1)
I want to:
m = SomeDecryptionAlgo(c3, using: e2)
Is this scenario (though quite strange) even possible? If so, does anyone know a googleable term or an algorithm/s which would fit my case?
Thanks in advance
Edit: The keypairs do not share the same modulus