An Efficient and Secure Event Signature EASES Protocol for PeertoPeer Massively Multiplayer Online G

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An Efficient and Secure Event Signature (EASES)
Protocol for Peer-to-Peer Massively Multiplayer
Online GamesMo-Che Chan, Shun-Yun Hu and
Jehn-Ruey JiangAdaptive Computing and
Networking Lab.National Central University
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Outline

• Background
• Related work
• NEO
• SEA
• The proposed scheme
• EASES
• Evaluation
• Conclusion

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Background - MMOG

• Multiplayer online game
• Massively multiplayer online game (MMOG)

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Background - architectures

• Client-server

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Background - architectures

• Server-cluster

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Background - architectures

• Peer-to-peer (P2P) network
• Efficiently maintain the topology
• Virtual environment

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Background game logic

• In client-server and server-cluster
• Server maintains game states
• Users send event to server
• Server sends information to player

round
time
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Background cheat problem

• Game logic is maintained by peers in P2P
  environments.
• Some players may gain advantages unfairly.

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Background - commitment

• Play the paper, scissors, rock game remotely
  without arbiter

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Background hash function

• Cryptographic hash function
• Strength depends on the following infeasibilities
• For any given hashed value, to find M or M
• For any given message M, to find H(M) H(M)
• To find any pair (M, M) such that H(M) H(M)

Hash function
010101110100
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Background - commitment

• No one can get unfair advantages if the hash
  function is secure.

H(Choice Random)
H(Choice Random)
Choice Random
Choice Random
First send H(Choice Random)
Then send (Choice Random)
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Background digital signature

• Concept

010101000111010011001011 010011100110101000110101
011010111000110101010100 110100011010101010101001
010101010010101010101010 ..
101001110100110010110110 101100110101000110101010
010111001011010101010011 010010110101010101010010
110110010101010101010111 ..
Signature algorithm
A document
To sign it
A digital signature

• No one can forge
• Signer cant repudiate that he executed the
  algorithm for this document
• Authenticity of the document

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Background digital signature

• To sign a message

To sign by senders private key
Hash function
message
0101101
1011110
message
1011110
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Background digital signature

• To verify a signature

message
1011110
To inverse the signature by signers public key
Hash function
?
0101101
0101101
To check they are the same or not
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Related work - NEO

• Every updating message
• Signing event updating message
• Encrypting the signed message
• After, send decrypting key

Player i
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Related work - SEA

• Every updating message
• Signed hash value of event updating message
• After, send the plain message

Player i
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The problem that we observed

• Digital signature algorithms are too slow.

To sign the message digest
Single Document
Hash algorithm
Signature algorithm
To produce the message digest
Original message
Signature
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The objective

• To efficiently sign many discrete messages

Message 1
Message 2

Message n
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The proposed EASES

• Initialization phase
• Every player prepares the keys for signing.
• Signing phase
• Every player signs his messages.
• Verification phase
• Every receiver verifies the authenticity.
• Re-initialization phase
• Re-generate new signing keys.

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EASES initialization phase
..
1011110
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EASES signing verification
.
Send out
j
j-1
j-2
j
j2
j1
j
j-1
j-2
j-1
j-2
j-3
.
j
j1
j2
j-1
j-2
j-3
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EASES re-initialization phase

• Re-execute initialization phase
• A more efficient way
• Reserve the last two keys

..
..
1011110
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Evaluation - performance

• Computational cost
• Hash replaces signature function
• Memory consumption
• 1,000 192 bits 24,000 bytes, when n 1,000
• Bandwidth consumption
• Length of Hash value is short than signatures

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Evaluation - security

• Unforgeability
• No one can claim that he signed M, unless he show
  the OSK of M.
• This requirement is secure if adopted
  cryptographic hash function is secure.
• Verifiability
• Hash function is public.

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Conclusion and discussion

• EASES is proposed to sign many discrete messages
  at once efficiently
• Security of EASES is as strong as those of
  traditional signature schemes
• ESAES implies the commitment property