Document or message security arrangements using a numerical hash function
First Claim
1. An apparatus which is arranged to process a selected part or selected parts of the text of a document or message to form a hash, the hash being of fewer characters than the selected part or parts of the text, the processing comprising retrieving numerical values which define the respective characters of the selected part or parts of the text and making a calculation using the numerical values of the successive characters of said selected part or parts of the text, the calculation made in respect of each said character using the result of the calculation made in respect of at least one previous character and also using one of a predetermined set of prime numbers, and each said calculation using an interim result to determine which of said set of prime numbers is used to continue that calculation.
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Abstract
A document or message is protected against forgery or repudiation by processing a selected part or parts of the text of the document or message to form a hash, usually of fewer characters than the selected part or parts of the text. The processing comprises retrieving numerical values which define the respective characters of the selected part or parts of the text and making a calculation using the numerical values of the successive characters. Preferably the hash is added to the text.
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Citations
18 Claims
- 1. An apparatus which is arranged to process a selected part or selected parts of the text of a document or message to form a hash, the hash being of fewer characters than the selected part or parts of the text, the processing comprising retrieving numerical values which define the respective characters of the selected part or parts of the text and making a calculation using the numerical values of the successive characters of said selected part or parts of the text, the calculation made in respect of each said character using the result of the calculation made in respect of at least one previous character and also using one of a predetermined set of prime numbers, and each said calculation using an interim result to determine which of said set of prime numbers is used to continue that calculation.
- 17. A process of forming a hash from a selected part or from selected parts of the text of a document or message, the process comprising retrieving numerical values which define the respective characters of the selected part or parts of said text and making a calculation using the numerical values of the successive characters of said selected part or parts of the text, the calculation in respect of each said character using the result of the calculation made in respect of at least one previous character and also using one of a predetermined set of prime numbers, wherein each said calculation uses an interim result to determine which of said set of prime numbers is used to continue the calculation, said hash being of fewer characters than said selected part or parts of the text.
Specification