Digital signature purpose encoding

A method of verifying a digital signature and a purpose description for a data stream comprising the steps of:

• passing said purpose description and said digital signature to an extended digital signature function;
• generating a first extended hash value using said purpose description;
• recovering a second extended hash value from said digital signature;
• and
• comparing said first extended hash value with said second extended hash value, a true comparison resulting in verifying that digital signature and said purpose description are valid.

A method for encoding a purpose description for a digital signature of a data stream in an electronic transaction, comprising the steps of:

• generating a hash value using a hash function on said data stream;
• passing said hash value and said purpose description to said hash function to generate an extended hash value;
• generating said extended digital signature by passing said extended hash value to a digital signature function wherein said digital signature function binds said purpose description with said digital signature;
• and
• affixing said extended digital signature to said input data stream to perform said electronic transaction.

In a network capable of handling an electronic transaction, an apparatus comprising:

• a client coupled to said network requesting said electronic transaction, said client sending a request over said network;
• a server coupled to said client, and to said network, said server receiving said request and sending an extended digital signature for authorizing said request, wherein a purpose description is binded in said extended digital signature;
• and
• an electronic transaction provider, said provider coupled to said network, said provider completing said electronic transaction in accordance with said purpose description of said authorization.