ZyXEL 35 Guia Do Utilizador

 

 

All contents copyright (c) 2006 ZyXEL Communications Corporation.   

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Users' public keys are published in an accessible directory. A person wishing to send an encrypted 

message uses the recipient's public key to scramble the information in the message. Only the 

recipient's private key can decrypt the message. 

So, if Bob wants to send a confidential message to Alice, his PKI software finds Alice's public key in 

the directory where it is published, and he uses it to encrypt his message. When Alice receives the 

encrypted message, she uses her private key to decrypt it. Because Alice keeps her private key secret, 

Bob can be assured that, even if his message were to be intercepted, only Alice can read it. 

 

 

 

Not to be confused with a digitized signature (a scan of a hand-written signature), a digital signature 

can be used with either encrypted or unencrypted messages to confirm the sender's identity and ensure 

the recipient that the message content has not been changed in transmission. Digital signatures 

incorporate the characteristics of hand-written signatures in that they can only be generated by the 

signer, are verifiable, and cannot easily be imitated or repudiated. 

 

 

Suppose that the famous Bob and Alice wish to correspond electronically. Bob wants to assure Alice 

that he originated the electronic message, and that its contents have not been tampered with. He does 

so by signing the message with a digital signature. 

When Bob clicks on the digital signature option on his e-mail application, special software applies a 

mathematical formula known as a hash function to the message, converting it to a fixed-length string 

of characters called a message digest. The digest acts as a "digital fingerprint" of the original message.