Alice’s phone
1. Alice writes a message to Bob
2. Her phone retrieves Bob’s public key from the server
and uses it to encrypt the message so only a phone with Bob’s private key can decrypt it
Encrypted
message
Server
Public keys are held on the server but private keys are only held by an owner’s phone
Anybody trying to intercept the message can’t decrypt it as they don’t have the private key from Bob’s phone
3. Bob’s phone receives the encrypted message
Encrypted
message
4. His phone has the correct private key
and so can decrypt
the message for Bob to read
Bob’s phone
Alice’s phone
Server
Bob’s phone
Encrypted message
1. Alice writes a message to Bob
2. Her phone retrieves Bob’s public key from the server
3. Bob’s phone receives the encrypted message
4. His phone has the correct private key
Public keys are held on the server but private keys are only held by an owner’s phone
and uses it to encrypt the message so only a phone with Bob’s private key can decrypt it
and so can decrypt
the message for Bob to read
Encrypted message
Anybody trying to intercept the message can’t decrypt it as they don’t have the private key from Bob’s phone