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Part 3  Implementation

Digital signatures

Digital signatures

 can be used to create commercial systems by using  public-  key encryp-

tion to achieve authentication: the merchant and purchaser can prove they are genuine. The 

purchaser’s digital signature is encrypted before sending a message using their private key 

and, on receipt, the public key of the purchaser is used to decrypt the digital signature. This 

proves the customer is genuine. Digital signatures are not widely used currently due to the 

difficulty of setting up transactions, but they will become more widespread as the  public-  key 

infrastructure (PKI) stabilises and use of certificate authorities increases.