TwoParty Generation of DSA Signature

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Two-Party Generation of DSA Signature

• Source CRYPTO 2001, LNCS 2139,
• pp.137154
• Authors Philip MacKenzie and Michael
• K. Reiter
• Speaker Ya-fen Chang
• Date 5/23/2002

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Outline

• Motivation
• DSA
• Preliminaries
• The Proposed Scheme

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1. Motivation

• Present an efficient and secure protocol by
• which two parties, each holding a share of a
• DSA private key, can interact to generate a
• DSA signature on a given message with respect
• to the corresponding public key.

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2. DSA

• qa prime factor of p-1
• Signer generates a random number kltq
• Private key is x, the public key is
• Signature (r,s)

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2. DSA con.

• Verification
• If vr, then the signature is verified

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3. Preliminaries
Signature
h SHA-1 Verification
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3. Preliminaries con.

• Mpk is the space of possible inputs to Epk.
• Mpk -v, v
• m1, m2, m1m2? Mpk
• Dsk(Epk(m1) pk (Epk(m2)) m1m2
• m1, m2, m1m2? Mpk
• Dsk(Epk(m1) ?pk m2) m1m2

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4. The Proposed Scheme

• 4-1 Initiation Phase
• Parties Alice and Bob
• xA /xB the private value held by Alice/Bob
• x xA xB mod q
• ygx mod p
• pk/sk the public/private key held by Alice
• pk/sk the public/private key held by Bob

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4-2 Signature Generation Phase
(1-1)
(1-2) ltz1, ?, ?gt
A
B
(2-1)
(2-2) r2
(3-1)
?zkp
(3-2) ltr, ?gt
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4-2 Signature Generation Phase con.1
A
B
(4-1)
(4-2) lt?, ??, ??gt
??zkp
sDsk(?) mod q lt(r mod q), sgt