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EPA-patent auf Extra-Info bei digitalen Signaturen
- To: email@example.com
- Subject: EPA-patent auf Extra-Info bei digitalen Signaturen
- From: PILCH Hartmut <firstname.lastname@example.org>
- Date: Mon, 6 Nov 2000 23:39:04 +0100 (CET)
- cc: email@example.com
- Comment: This message comes from the debate mailing list.
- Sender: firstname.lastname@example.org
Public key/signature cryptosystem with enhanced digital signature certification.
FISCHER ADDISON M
1. In a communications system having a plurality of terminal devices
(Terminals A to N) coupled to an insecure communications channel (12)
over which users of said terminal devices may exchange private
messages, each of said user's having a public key (30) and an
associated private key (32), an improved method of digitally signing
and certifying a message to be transmitted characterized by the steps
formulating at least a portion of a digital message (20);
digitally signing said message (40); and
including within said message an authorizing certificate (28, 116)
which specifies the authority which has been granted to the signer of
2. A method according to claim 1, further including the step of
providing at least one field in said message identifying the nature of
the digital data being transmitted (22).
3. A method according to claim 1, wherein the formulating step
includes the step of providing a field allowing the user to insert a
predetermined comment (26) regarding the data being transmitted.
4. A method according to claim 1, further including the step of
applying a hashing function (34) to at least a portion of the message
to be transmitted to form a presignature hash (36); and wherein said
digitally signing step includes the step of decrypting said
presignature hash with said private decrypting key (32) to form said
5. A method according to claim 4, further including the step of
forming a digital signature packet (42) comprising the digital
signature and a representation of said at least a portion of the
message to be transmitted.
6. A method according to claim 1, wherein said authorizing certificate
(116) defines the cosignature requirements which must accompany the
7. A method according to claim 6, wherein a digital signature by a
third party indicating approval of the user's signature is required
(116) thereby defining a counter signature requirement.
8. A method according to claim 7, wherein the third party countersigns
(86) by digitally signing the sender's digital signature.
9. A method according to claim 6, wherein the step of defining
cosignature requirements includes the step of specifying at least one
other digital signature which is required to appear in the digital
message thereby defining a joint signature requirement (116).
10. A method according to claim 1, wherein said authorizing
certificate defines limitations as to the authority granted by the
11. A method according to claim 10, further including the step of
setting a monetary limit for the sender.
12. A method according to claim 1, wherein said authorizing
certificate includes at least one field indicative of the degree of
responsibility delegated to the sender.
13. A method according to claim 1, wherein said authorizing
certificate defines a hierarchy of certificates within the transmitted
message such that a recipient of the message can verify the authority
of the signer based upon an analysis of the signed message.
Data supplied from the esp@cenet database - l2
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