Re: [viff-devel] [issue80] Broadcast

2009-03-10 Thread Ivan Bjerre Damgård 

Quoting Janus Dam Nielsen :

In the simple case I want to shout out a number to everybody, even  
somebody who is eavesdropping.


But secrecy of what you shout is not the real problem. The problem is  
to make sure everyone agrees on what was said. This is not obvious in  
the case where people may not follow the protocol. For instance, if  
you want a solution that does not depend on computational assumptions,  
then if a third or more of the players are corrupt, then there is NO  
solution.


Think of 3 players A,B and C, where A wants to broadcast a message,  
say 0 or 1. One player may be corrupt. So A is supposed to send a bit  
b to both B and C. Say B hears 0 from A. He doesn't know if A said the  
same to C. He can ask C what he heard, but if C says "A said 1 to me",  
there is no way to tell if A or C is lying..


regards, Ivan




--
Janus


Den 10/03/2009 kl. 12.23 skrev Ivan Bjerre Damgård:

It can definitely be useful to have a broadcast method, for  
instance to complete the implementation of the asynchronous  
maliciously secure protocol, we will need broadcast.


But one needs to be careful about what kind of security we want.  
There is a whole jungle of protocols, depending on whether it is  
unconditional or computational security, synchronous or  
asynchronous network, and what number of players you assume can be  
corrupt. I think a protocol of Bracha has in fact already been  
implemented in VIFF


regards, Ivan

Quoting Janus Dam Nielsen :



New submission from Janus Dam Nielsen :

I would like to see a broadcast method in the Runtime class. The
purpose of the broadcast method should be to distribute a public value
among all parties (or some subset of parties).

A case: All parties in a computation needs to read a value from
standard in, and it is a different value for each party. We want to
tell the value to everybody else.

An example use could be like the input method:
a,b,c = runtime.broadcast([1,2,3], value)

Similarly, broadcast can be used in a conditional if only some subset
of parties wants to distribute a value.

--
assignedto: mg
messages: 310
nosy: jdn, mas, mg
status: chatting
title: Broadcast
type: wish


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Re: [viff-devel] [issue80] Broadcast

2009-03-10 Thread Janus Dam Nielsen 
In the simple case I want to shout out a number to everybody, even  
somebody who is eavesdropping.


--
Janus


Den 10/03/2009 kl. 12.23 skrev Ivan Bjerre Damgård:

It can definitely be useful to have a broadcast method, for  
instance to complete the implementation of the asynchronous  
maliciously secure protocol, we will need broadcast.


But one needs to be careful about what kind of security we want.  
There is a whole jungle of protocols, depending on whether it is  
unconditional or computational security, synchronous or  
asynchronous network, and what number of players you assume can be  
corrupt. I think a protocol of Bracha has in fact already been  
implemented in VIFF


regards, Ivan

Quoting Janus Dam Nielsen :



New submission from Janus Dam Nielsen :

I would like to see a broadcast method in the Runtime class. The
purpose of the broadcast method should be to distribute a public  
value

among all parties (or some subset of parties).

A case: All parties in a computation needs to read a value from
standard in, and it is a different value for each party. We want to
tell the value to everybody else.

An example use could be like the input method:
a,b,c = runtime.broadcast([1,2,3], value)

Similarly, broadcast can be used in a conditional if only some subset
of parties wants to distribute a value.

--
assignedto: mg
messages: 310
nosy: jdn, mas, mg
status: chatting
title: Broadcast
type: wish


VIFF Issue Tracker 


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Re: [viff-devel] [issue80] Broadcast

2009-03-10 Thread Mikkel Krøigård 

Citat af Ivan Bjerre Damgård :

It can definitely be useful to have a broadcast method, for instance  
to complete the implementation of the asynchronous maliciously  
secure protocol, we will need broadcast.


But one needs to be careful about what kind of security we want.  
There is a whole jungle of protocols, depending on whether it is  
unconditional or computational security, synchronous or asynchronous  
network, and what number of players you assume can be corrupt. I  
think a protocol of Bracha has in fact already been implemented in  
VIFF


Indeed it has. It's located in the active runtime (active.py).
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Re: [viff-devel] [issue80] Broadcast

2009-03-10 Thread Ivan Bjerre Damgård 
It can definitely be useful to have a broadcast method, for instance  
to complete the implementation of the asynchronous maliciously secure  
protocol, we will need broadcast.


But one needs to be careful about what kind of security we want. There  
is a whole jungle of protocols, depending on whether it is  
unconditional or computational security, synchronous or asynchronous  
network, and what number of players you assume can be corrupt. I think  
a protocol of Bracha has in fact already been implemented in VIFF


regards, Ivan

Quoting Janus Dam Nielsen :



New submission from Janus Dam Nielsen :

I would like to see a broadcast method in the Runtime class. The
purpose of the broadcast method should be to distribute a public value
among all parties (or some subset of parties).

A case: All parties in a computation needs to read a value from
standard in, and it is a different value for each party. We want to
tell the value to everybody else.

An example use could be like the input method:
a,b,c = runtime.broadcast([1,2,3], value)

Similarly, broadcast can be used in a conditional if only some subset
of parties wants to distribute a value.

--
assignedto: mg
messages: 310
nosy: jdn, mas, mg
status: chatting
title: Broadcast
type: wish


VIFF Issue Tracker 


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[viff-devel] [issue80] Broadcast

2009-03-10 Thread Janus Dam Nielsen 

New submission from Janus Dam Nielsen :

I would like to see a broadcast method in the Runtime class. The 
purpose of the broadcast method should be to distribute a public value 
among all parties (or some subset of parties).

A case: All parties in a computation needs to read a value from 
standard in, and it is a different value for each party. We want to 
tell the value to everybody else.

An example use could be like the input method:
a,b,c = runtime.broadcast([1,2,3], value)

Similarly, broadcast can be used in a conditional if only some subset 
of parties wants to distribute a value.

--
assignedto: mg
messages: 310
nosy: jdn, mas, mg
status: chatting
title: Broadcast
type: wish


VIFF Issue Tracker 


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