Digital signature system and apparatus
First Claim
1. Digital signature apparatus comprising,a cryptographic engine having an input for a key, an input for a data word to be enciphered, and an output for enciphered data, and means for selectively supplying a master key to the engine,means cooperating with said engine for forming a sequence of signature key tables by enciphering selected data under the master key, a signature key table having a zero signature key and a one key for each bit of a compressed encoding of predetermined length of a message for which a signature is to be formed,means cooperating with said engine for forming a last validation table for a last of the signature key tables in the sequence by encoding selected data under each of the signature keys of the last signature key table, the last validation table having an entry for each signature key of the corresponding signature key table,means for cryptographically forming a compressed encoding of the last validation table, the compressed encoding having the length of the data input of said engine, and for forming a validation table for each other signature key table by enciphering a function of the compressed encoding of the next validation table in the sequence under the keys of a signature key table,whereby the compressed encoding of the first validation table is a cryptographic function of each signature key table and each validation table.
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Abstract
A digital signature machine provides a simplified method of forming and verifying a signature that is appended to a digital message. A sender transmits a signature with the usual signature keys and with validation table entries that correspond to the unsent keys and with the compressed encoding of the next validation table. The receiver uses the compressed encoding of the next validation table to form validation table entries from the signature keys so that the receiver has a full validation table. This validation table is compressed and compared with the compressed encoding which was received from the sender in a preceding message.
55 Citations
6 Claims
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1. Digital signature apparatus comprising,
a cryptographic engine having an input for a key, an input for a data word to be enciphered, and an output for enciphered data, and means for selectively supplying a master key to the engine, means cooperating with said engine for forming a sequence of signature key tables by enciphering selected data under the master key, a signature key table having a zero signature key and a one key for each bit of a compressed encoding of predetermined length of a message for which a signature is to be formed, means cooperating with said engine for forming a last validation table for a last of the signature key tables in the sequence by encoding selected data under each of the signature keys of the last signature key table, the last validation table having an entry for each signature key of the corresponding signature key table, means for cryptographically forming a compressed encoding of the last validation table, the compressed encoding having the length of the data input of said engine, and for forming a validation table for each other signature key table by enciphering a function of the compressed encoding of the next validation table in the sequence under the keys of a signature key table, whereby the compressed encoding of the first validation table is a cryptographic function of each signature key table and each validation table.
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6. A method for forming a digital signature in a sequence of digital signatures, comprising,
compressing a message to a predetermined length, selecting signature keys from a signature key table to code the compressed message, forming a validation table by encoding a function of the compressed encoding of the next validation table in the sequence under each of the signature keys of the signature key table, and transmitting as the signature the selected signature keys, the entries of the validation table for the unselected keys, and the compressed encoding of the next validation table.
Specification