Fairdice : Crypto : Protocol : v0.3 : Game Specific : Client-Server

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Fairdice Protocol v0.3 : Game Specific : Client-Server


[Definition]

GAME_MESSAGE
 = 
"G " GAME_STR " | P " PROTOCOL_STR


GAME_STR
 = 
GAME_ID



 ; 
this identifies the particular game instance being played


PROTOCOL_STR
 = 
GAME_INIT | GAME_RAND | GAME_GENR | GAME_VERI



 ; 
these stages must be played in order, each sequence
    happening once.

Stage	Initiator	Description
GAME_INIT	Client	Initialise the game.
GAME_RAND	Client	The client decides to play and provides their random input
GAME_GENR	Server	Once the server has everyone's input, generate the output
GAME_VERI	Server	Once the server announces the output, verify it is fair

Definitions


[Definition]

MODULO
 = 
1*200(HEX)



 ; 
The number of faces on the die.
       The number of events between which we are selecting.


SHAREDTEXT
 = 
HOST_ID " ^ " GAME_ID " ^ " TIMESTAMP " ^ " PADDING " ^ "


PADDING
 = 
*(HEX)



 ; 
The length of the PADDING is selected to make the
       length of the SHAREDTEXT up to 250 characters long.


USERTEXT
 = 
250(HEX)


PLAINTEXT
 = 
SHAREDTEXT USERTEXT


DIGEST
 = 
<the tiger hash of PLAINTEXT, displayed as a HEX string>


INPUT
 = 
<USERTEXT modulo MODULO displayed in HEX>


OUTPUT
 = 
<the sum of the INPUTs from the host and players, modulo MODULO>


[Example]

MODULO
 = 
"6"


SHAREDTEXT
 = 
"Richard.Com ^ testgame3 ^ 2004-08-16 15:36:36 ^ 1B3011378D
    689FDC04C2C42806C7324E462FF9ED64BC9D55782C112DF20EA47B31C359
    AE3AECDD9598D966DAD54DA5ABB1BE010D36AC090259B4E3BC5CA86A194F
    8FD1D931C7999E3EAD90A1911054E4C5D7D07837DDFD033F6726B3D5B5C6
    7DE3F96D8 ^ "


USERTEXT 1
 = 
"5217E55D13401F7CB3C644B5ECBA87880E14D70E1A83A92F4059828AD67
    6024EE4FA8BB429805A4B2C981A6D66E1BA9C93C2D4C3D93A5E01ED459A4
    B604CD71375A00F7A6473594731207AF9412C199E7C18F6BDB1E7A9EACCB
    8395B45D7735C15A9EEB4D990538FD3A2CF4CD223495BABF1FC5C5D26062
    D46E8E65282"


USERTEXT 2
 = 
"79FA03B7AB26EDE078CA59FCB7FC3D9D5B80EBEED6F0DCBDE4B5AF6CB0B
    E85A0ECB422E78FA5D94D27E88D0B8B532D6EA23088B7C612FBF0E2ED47A
    6B8920C3AA263D52D76E6C6B21AD017A407D6B5080324BA0E26826194540
    E0423ADA4B2C2CD47ECAD87826AE6AD984FA8A1E4AC1094BA20B8E27422E
    5F671D3868D"


PLAINTEXT 1
 = 
"Richard.Com ^ testgame3 ^ 2004-08-16 15:36:36 ^ 1B3011378D6
    89FDC04C2C42806C7324E462FF9ED64BC9D55782C112DF20EA47B31C359A
    E3AECDD9598D966DAD54DA5ABB1BE010D36AC090259B4E3BC5CA86A194F8
    FD1D931C7999E3EAD90A1911054E4C5D7D07837DDFD033F6726B3D5B5C67
    DE3F96D8 ^ 5217E55D13401F7CB3C644B5ECBA87880E14D70E1A83A92F4
    059828AD676024EE4FA8BB429805A4B2C981A6D66E1BA9C93C2D4C3D93A5
    E01ED459A4B604CD71375A00F7A6473594731207AF9412C199E7C18F6BDB
    1E7A9EACCB8395B45D7735C15A9EEB4D990538FD3A2CF4CD223495BABF1F
    C5C5D26062D46E8E65282"


PLAINTEXT 2
 = 
"Richard.Com ^ testgame3 ^ 2004-08-16 15:36:36 ^ 1B3011378D6
    89FDC04C2C42806C7324E462FF9ED64BC9D55782C112DF20EA47B31C359A
    E3AECDD9598D966DAD54DA5ABB1BE010D36AC090259B4E3BC5CA86A194F8
    FD1D931C7999E3EAD90A1911054E4C5D7D07837DDFD033F6726B3D5B5C67
    DE3F96D8 ^ 79FA03B7AB26EDE078CA59FCB7FC3D9D5B80EBEED6F0DCBDE
    4B5AF6CB0BE85A0ECB422E78FA5D94D27E88D0B8B532D6EA23088B7C612F
    BF0E2ED47A6B8920C3AA263D52D76E6C6B21AD017A407D6B5080324BA0E2
    6826194540E0423ADA4B2C2CD47ECAD87826AE6AD984FA8A1E4AC1094BA2
    0B8E27422E5F671D3868D"


DIGEST 1
 = 
"06F5E826BE31B56979D88786FE26E7BD5F77497880136916"


DIGEST 2
 = 
"BD0C27F25CA874E52C40BE3D0C0602208F845F9A3E18C4F2"


INPUT 1
 = 
"2"


INPUT 2
 = 
"1"


OUTPUT
 = 
"3"



(So in this case, the die rolled a "3")

(You can use the Gnu Multiple Precision Website to verify the calculations.)

Stage : Initialisation


[Definition]

GAME_INIT
 = 
INIT_REQUEST | INIT_RESPONSE | INIT_SEED | INIT_MODULO


INIT_REQUEST
 = 
"join request"


INIT_RESPONSE
 = 
"join respond " JOIN_ANSWER


INIT_SEED
 = 
"seed " SHAREDTEXT


INIT_MODULO
 = 
"modulo " MODULO


JOIN_ANSWER
 = 
"yes" | "no HOST_UNAVAILABLE" | "no GAME_UNAVAILABLE" |
    ("no HOST_MESSAGE " DISPLAY_STR ) | ("SERVER_MESSAGE " DISPLAY_STR )


[Sequence]
There are two valid sequences.


client to server : INIT_REQUEST
server to client : INIT_RESPONSE (negative)

or

client to server : INIT_REQUEST
server to client : INIT_RESPONSE (positive)
server to client : INIT_SEED
server to client : INIT_MODULO

[Sequence]
There are two valid sequences. client to server : INIT_REQUEST server to client : INIT_RESPONSE (negative) or client to server : INIT_REQUEST server to client : INIT_RESPONSE (positive) server to client : INIT_SEED server to client : INIT_MODULO

Stage : Randomisation


[Definition]

GAME_RAND
 = 
RAND_REVEAL | RAND_ID


RAND_REVEAL
 = 
"digest reveal " DIGEST


RAND_ID
 = 
"id " PLAYER_ID


[Sequence]
There is one valid sequences.

client to server : RAND_REVEAL
server to client : RAND_ID

[Sequence]
There is one valid sequences. client to server : RAND_REVEAL server to client : RAND_ID

Stage : Generation


[Definition]

GAME_GENR
 = 
GENR_SIZE | GENR_REQUEST | GENR_RESPOND | GENR_REVEAL


GENR_SIZE
 = 
"size " GAME_SIZE


GENR_REQUEST
 = 
"digest request " PLAYER_RANGE


GENR_RESPOND
 = 
"digest respond " PLAYER_ID " " DIGEST


GENR_REVEAL
 = 
"usertext reveal " USERTEXT


PLAYER_RANGE
 = 
INT_RANGE


[Sequence]
There is one general sequences.

server to client : GENR_SIZE
client to server : GENR_REQUEST
server to client : GENR_RESPOND
client to server : GENR_REVEAL

however steps 2 and 3 may happen several times until the
client is satisfied that it has all the digests it wants.

[Sequence]
There is one general sequences. server to client : GENR_SIZE client to server : GENR_REQUEST server to client : GENR_RESPOND client to server : GENR_REVEAL however steps 2 and 3 may happen several times until the client is satisfied that it has all the digests it wants.


[Example]
Let's assume we are player 1 in a 4 player game (remember that
means there are 5 participants, because the host is participant 0).

For brevity I am truncating the digests.


GENR_SIZE
 = 
"P size 4"


GENR_REQUEST
 = 
"P digest request 0,2-3"


GENR_RESPONSE
 = 
"P digest respond 0 DEADBEEF1234..."


GENR_RESPONSE
 = 
"P digest respond 2 DEADBEEF4567..."


GENR_RESPONSE
 = 
"P digest respond 3 DEADBEEF7890..."


GENR_REQUEST
 = 
"P digest request 4"


GENR_RESPONSE
 = 
"P digest respond 0 DECAFBAD6667..."



 ; 
ok, we now have them all


GENR_REVEAL
 = 
"P usertext reveal 83E7728F3747..."

Stage : Verification


[Definition]

GAME_VERI
 = 
VERI_OUTCOME | VERI_REQUEST | VERI_RESPOND | VERI_FINISH 
    | VERI_CLOSING | VERI_CLOSED


VERI_OUTCOME
 = 
"outcome " OUTCOME


VERI_REQUEST
 = 
"usertext request " PLAYER_RANGE


VERI_RESPOND
 = 
"usertext respond " PLAYER_ID " " USERTEXT


VERI_FINISH
 = 
"finish " ( "fair" | ("fail " DISPLAY_STR) | ("fraud " DISPLAY_STR) )


VERI_CLOSING
 = 
"closing"


VERI_CLOSED
 = 
"closed"


[Sequence]
There is one general sequence.

server to client : VERI_OUTCOME
client to server : VERI_REQUEST
server to client : VERI_RESPOND
client to server : VERI_FINISH
client to server : VERI_CLOSING
server to client : VERI_CLOSED

however be aware:

Either side can send VERI_CLOSING at any stage of a game.
If it is sent before stage VERI, it cancels the game, triggering
a VERI_FINISH (fail) being sent to everyone.

As with stage GENR, steps 2 and 3 can be repeated until the client
is happy it has all the usertexts and is able to calculate for
itself the outcome, to compare with the one the server told it.

If a usertext it gets told in this stage does not match a digest
from that player it was told in the previous stage, it calls "fraud".

[Sequence]
There is one general sequence. server to client : VERI_OUTCOME client to server : VERI_REQUEST server to client : VERI_RESPOND client to server : VERI_FINISH client to server : VERI_CLOSING server to client : VERI_CLOSED however be aware: Either side can send VERI_CLOSING at any stage of a game. If it is sent before stage VERI, it cancels the game, triggering a VERI_FINISH (fail) being sent to everyone. As with stage GENR, steps 2 and 3 can be repeated until the client is happy it has all the usertexts and is able to calculate for itself the outcome, to compare with the one the server told it. If a usertext it gets told in this stage does not match a digest from that player it was told in the previous stage, it calls "fraud".

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