DistOS-2011W Wuala - Revision history

Lmundt: /* Security */

2011-03-09T13:57:19Z

Security

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	Wuala was designed with security as another primary goal. All files are encrypted on the client system with 128-bit AES before being fragmented and stored in the Wuala cloud. This allows the client's system to provide all the computation resources for decrypting and encrypting and it also provides additional security as the user's password which is encrypted with 2048 bit RSA never leaves the client's system.		Wuala was designed with security as another primary goal. All files are encrypted on the client system with 128-bit AES before being fragmented and stored in the Wuala cloud. This allows the client's system to provide all the computation resources for decrypting and encrypting and it also provides additional security as the user's password which is encrypted with 2048 bit RSA never leaves the client's system.

	Wuala also allows users to share their files with different levels of granularity. These levels are user, group, and world. These permissions exist within the metadata that is stored with the fragments. One potential leak of information that could occur is that users who have access to shared files could potentially see who else has access to the same files. This information leakage has been accounted for an Wuala's underlying enrypted file system cryptree<ref> Gromilund Dominik, Meisser Luzius, Schmid Stefan, Wattenhofer Roger. 2006. Cryptree: A Folder Tree Structure for Cryptographic File Systems. ''Computer Engineering and Networks Laboratory, ETH Zurich. http:/~~/dcg.ethz.ch/publications/srds06.pdf</ref~~> is designed to avoid this potential security hole.		Wuala also allows users to share their files with different levels of granularity. These levels are user, group, and world. These permissions exist within the metadata that is stored with the fragments. One potential leak of information that could occur is that users who have access to shared files could potentially see who else has access to the same files. This information leakage has been accounted for an Wuala's underlying enrypted file system cryptree<ref name="cryptree"/> is designed to avoid this potential security hole.

	Routing is a potential source of attack. Super nodes are drawn from the client population as such it is possible for a malicious user to reverse engineer the method of election and set up a subset of super nodes. In a traditional routing system the super nodes would have static routes often only knowing about their immediate neighbours, this could leave the system susceptible to a partition attack as the a malicious user could remove all there super nodes at once thus fracturing the network. Wuala's routing doesn't consist solely of the immediate neighbours or any other static information. While Wuala's routing does contain immediate neighbours it also includes a number of random super nodes. These randomly connected super nodes also change over time as all requests contain routing information that can be examined by any routing super nodes. The routing super nodes can in turn opt to add a connection to any of the super nodes mentioned in this information and do so periodically.		Routing is a potential source of attack. Super nodes are drawn from the client population as such it is possible for a malicious user to reverse engineer the method of election and set up a subset of super nodes. In a traditional routing system the super nodes would have static routes often only knowing about their immediate neighbours, this could leave the system susceptible to a partition attack as the a malicious user could remove all there super nodes at once thus fracturing the network. Wuala's routing doesn't consist solely of the immediate neighbours or any other static information. While Wuala's routing does contain immediate neighbours it also includes a number of random super nodes. These randomly connected super nodes also change over time as all requests contain routing information that can be examined by any routing super nodes. The routing super nodes can in turn opt to add a connection to any of the super nodes mentioned in this information and do so periodically.

Lmundt: /* Speed */

2011-03-09T13:56:27Z

Speed

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	Minimizing write times is another way of ensuring fast access. This is one reason the designers of Wuala went with erasure codes for the fragments of data. Replication would cause the entire file to be copied a number of times across the Wuala cloud. This would increase the amount of time for a write to finish and maintenance actions to complete. Erasure codes decrease the amount of data that needs to be stored to provide reliable storage.		Minimizing write times is another way of ensuring fast access. This is one reason the designers of Wuala went with erasure codes for the fragments of data. Replication would cause the entire file to be copied a number of times across the Wuala cloud. This would increase the amount of time for a write to finish and maintenance actions to complete. Erasure codes decrease the amount of data that needs to be stored to provide reliable storage.

	While files are on a storage node they are residing in untrusted storage. The fragments are encrypted and as such reside in an encrypted file system on the storage node. Wuala has access rights similar to other files systems but most cryptographic storage methods make changing these rights very slow and entire portions of the file system need to be re-encrypted <ref> Gromilund Dominik, Meisser Luzius, Schmid Stefan, Wattenhofer Roger. 2006. Cryptree: A Folder Tree Structure for Cryptographic File Systems. ''Computer Engineering and Networks Laboratory, ETH Zurich. http://dcg.ethz.ch/publications/srds06.pdf</ref>. The designers of Wuala have designed a hierarchical encrypted file system that allows the changing of permissions in constant time by allowing the permissions to be inheritable in the structure.		While files are on a storage node they are residing in untrusted storage. The fragments are encrypted and as such reside in an encrypted file system on the storage node. Wuala has access rights similar to other files systems but most cryptographic storage methods make changing these rights very slow and entire portions of the file system need to be re-encrypted <ref name="cryptree"> Gromilund Dominik, Meisser Luzius, Schmid Stefan, Wattenhofer Roger. 2006. Cryptree: A Folder Tree Structure for Cryptographic File Systems. ''Computer Engineering and Networks Laboratory, ETH Zurich. http://dcg.ethz.ch/publications/srds06.pdf</ref>. The designers of Wuala have designed a hierarchical encrypted file system that allows the changing of permissions in constant time by allowing the permissions to be inheritable in the structure.

	Routing is the last significant area that the designers of Wuala focused on to obtain speed. Wuala's routing can be thought of a structure overlay network<ref> Gromilund Dominik, Miller Peter. 2007. A Pattern Language for Overlay Networks in Peer-to-Peer Systems. ''Department of Computer Science, ETH Zurich. http://people.inf.ethz.ch/lehnerh/pm/publications/getpdf.php?bibname=Own&id=GrolimundMueller06.pdf</ref> which is a system that given a key finds the node that contains the information associated with that key. In Wuala the routing table stores paths between super nodes. Each super node is connected to it's immediate neighbours but additionally each super node is connected to some randomly selected super nodes. These random connections reduce the amount of hops it takes for a request to get routed to O(log n) where n is the number of super nodes in the system.		Routing is the last significant area that the designers of Wuala focused on to obtain speed. Wuala's routing can be thought of a structure overlay network<ref name="language"> Gromilund Dominik, Miller Peter. 2007. A Pattern Language for Overlay Networks in Peer-to-Peer Systems. ''Department of Computer Science, ETH Zurich. http://people.inf.ethz.ch/lehnerh/pm/publications/getpdf.php?bibname=Own&id=GrolimundMueller06.pdf</ref> which is a system that given a key finds the node that contains the information associated with that key. In Wuala the routing table stores paths between super nodes. Each super node is connected to it's immediate neighbours but additionally each super node is connected to some randomly selected super nodes. These random connections reduce the amount of hops it takes for a request to get routed to O(log n) where n is the number of super nodes in the system.

	== Security ==		== Security ==

Lmundt: /* Fairness */

2011-03-09T13:55:23Z

Fairness

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	1GB of storage in the Wuala cloud is granted upon registration. Users with sufficient uptime can volunteer additional storage on any system that uses their credentials. The amount of storage granted on the Wuala cloud is ( storage volunteered x uptime ) so to both storage and uptime are rewarded as a product of the other. An interesting property of the Wuala system is a single user can have one or many system tied to their account. They can in turn have one or more systems volunteering storage and the storage granted to the user would be the sum of the all the contributing node's ( storage x uptime ) products.		1GB of storage in the Wuala cloud is granted upon registration. Users with sufficient uptime can volunteer additional storage on any system that uses their credentials. The amount of storage granted on the Wuala cloud is ( storage volunteered x uptime ) so to both storage and uptime are rewarded as a product of the other. An interesting property of the Wuala system is a single user can have one or many system tied to their account. They can in turn have one or more systems volunteering storage and the storage granted to the user would be the sum of the all the contributing node's ( storage x uptime ) products.

	Measuring uptime and contributed storage are relatively simple and can be made difficult to falsify the last dimension of contribution: bandwidth can be harder to quantify. This is because the other two are easy to quantify and bandwidth needs to be qualified. To qualify the level of bandwidth contribution Wuala relies on a reputation system for storage nodes. This process of reputation monitoring is done in five steps<ref name="reputation"/>:		Measuring uptime and contributed storage are relatively simple and can be made difficult to falsify the last dimension of contribution: bandwidth can be harder to quantify. This is because the other two are easy to quantify and bandwidth needs to be qualified. To qualify the level of bandwidth contribution Wuala relies on a reputation system for storage nodes. This process of reputation monitoring is done in five steps<ref name="reputation"> Gromilund Dominik, Meisser Luzius, Schmid Stefan, Wattenhofer Roger. 2006. Havelaar: A Robust and Efficient Reputation System for Active Peer-to-Peer Systems. ''Computer Engineering and Networks Laboratory, ETH Zurich. http://dcg.ethz.ch/publications/netecon06.pdf</ref>:
	# Every node keeps records of the amount of bandwidth of all the nodes that it conducts transactions with.		# Every node keeps records of the amount of bandwidth of all the nodes that it conducts transactions with.
	# Periodically the nodes report to their observations to their immediate neighbours.		# Periodically the nodes report to their observations to their immediate neighbours.

Lmundt: /* Fairness */

2011-03-09T13:54:45Z

Fairness

← Older revision		Revision as of 13:54, 9 March 2011
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	1GB of storage in the Wuala cloud is granted upon registration. Users with sufficient uptime can volunteer additional storage on any system that uses their credentials. The amount of storage granted on the Wuala cloud is ( storage volunteered x uptime ) so to both storage and uptime are rewarded as a product of the other. An interesting property of the Wuala system is a single user can have one or many system tied to their account. They can in turn have one or more systems volunteering storage and the storage granted to the user would be the sum of the all the contributing node's ( storage x uptime ) products.		1GB of storage in the Wuala cloud is granted upon registration. Users with sufficient uptime can volunteer additional storage on any system that uses their credentials. The amount of storage granted on the Wuala cloud is ( storage volunteered x uptime ) so to both storage and uptime are rewarded as a product of the other. An interesting property of the Wuala system is a single user can have one or many system tied to their account. They can in turn have one or more systems volunteering storage and the storage granted to the user would be the sum of the all the contributing node's ( storage x uptime ) products.

	Measuring uptime and contributed storage are relatively simple and can be made difficult to falsify the last dimension of contribution: bandwidth can be harder to quantify. This is because the other two are easy to quantify and bandwidth needs to be qualified. To qualify the level of bandwidth contribution Wuala relies on a reputation system for storage nodes. This process of reputation monitoring is done in five steps:		Measuring uptime and contributed storage are relatively simple and can be made difficult to falsify the last dimension of contribution: bandwidth can be harder to quantify. This is because the other two are easy to quantify and bandwidth needs to be qualified. To qualify the level of bandwidth contribution Wuala relies on a reputation system for storage nodes. This process of reputation monitoring is done in five steps<ref name="reputation"/>:
	# Every node keeps records of the amount of bandwidth of all the nodes that it conducts transactions with.		# Every node keeps records of the amount of bandwidth of all the nodes that it conducts transactions with.
	# Periodically the nodes report to their observations to their immediate neighbours.		# Periodically the nodes report to their observations to their immediate neighbours.

Lmundt: /* Fairness */

2011-03-09T13:54:12Z

Fairness

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	== Fairness ==		== Fairness ==

	As a system that relies on the contributions of it's users Wuala needs methods to encourage contribution and deter freeloading. Users's contributions are measured in three main dimensions: uptime, storage, and bandwidth.		As a system that relies on the contributions of it's users Wuala needs methods to encourage contribution and deter freeloading. Users's contributions are measured in three main dimensions: uptime, storage, and bandwidth<ref name="video"/>.

	First is sufficient uptime. To keep the total number of fragments at a reasonable number while ensure reliable recovery Wuala needs an average uptime from each storage and super node at 17% which is approximately four hours. Wuala rewards users whose node(s) exceed the minimum uptime as seen in storage.		First is sufficient uptime. To keep the total number of fragments at a reasonable number while ensure reliable recovery Wuala needs an average uptime from each storage and super node at 17% which is approximately four hours. Wuala rewards users whose node(s) exceed the minimum uptime as seen in storage.

Lmundt: /* References */

2011-03-09T13:53:01Z

References

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	=References=		=References=

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	<ref name="cryptree"> Gromilund Dominik, Meisser Luzius, Schmid Stefan, Wattenhofer Roger. 2006. Cryptree: A Folder Tree Structure for Cryptographic File Systems. ''Computer Engineering and Networks Laboratory, ETH Zurich. http://dcg.ethz.ch/publications/srds06.pdf</ref>		<ref name="cryptree"> Gromilund Dominik, Meisser Luzius, Schmid Stefan, Wattenhofer Roger. 2006. Cryptree: A Folder Tree Structure for Cryptographic File Systems. ''Computer Engineering and Networks Laboratory, ETH Zurich. http://dcg.ethz.ch/publications/srds06.pdf</ref>

Lmundt: /* References */

2011-03-09T13:52:27Z

References

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	=References=		=References=

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	<ref name="cryptree"> Gromilund Dominik, Meisser Luzius, Schmid Stefan, Wattenhofer Roger. 2006. Cryptree: A Folder Tree Structure for Cryptographic File Systems. ''Computer Engineering and Networks Laboratory, ETH Zurich. http://dcg.ethz.ch/publications/srds06.pdf</ref>		<ref name="cryptree"> Gromilund Dominik, Meisser Luzius, Schmid Stefan, Wattenhofer Roger. 2006. Cryptree: A Folder Tree Structure for Cryptographic File Systems. ''Computer Engineering and Networks Laboratory, ETH Zurich. http://dcg.ethz.ch/publications/srds06.pdf</ref>
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	<ref name="video"> Gromilund Dominik. 2007. Wuala - A Distributed File System. ''Computer Engineering and Networks Laboratory, ETH Zurich. http://www.youtube.com/watch?v=3xKZ4KGkQY8</ref>		<ref name="video"> Gromilund Dominik. 2007. Wuala - A Distributed File System. ''Computer Engineering and Networks Laboratory, ETH Zurich. http://www.youtube.com/watch?v=3xKZ4KGkQY8</ref>

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	<references/>		<references/>

Lmundt: /* Speed */

2011-03-09T13:51:26Z

Speed

← Older revision		Revision as of 13:51, 9 March 2011
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	== Speed ==		== Speed ==
	One of the primary design goals of Wuala is speed. The designers of Wuala wanted a way for files to be recovered from multiple sources allowing parallel downloads. The designer's of Wuala decided to store files as a number of fragments across the Wuala cloud as this would provide the data in a manner that would allow concurrent access<ref> Gromilund Dominik. 2007. Wuala - A Distributed File System. ''Computer Engineering and Networks Laboratory, ETH Zurich. http://www.youtube.com/watch?v=3xKZ4KGkQY8</ref>.		One of the primary design goals of Wuala is speed. The designers of Wuala wanted a way for files to be recovered from multiple sources allowing parallel downloads. The designer's of Wuala decided to store files as a number of fragments across the Wuala cloud as this would provide the data in a manner that would allow concurrent access<ref name="video"> Gromilund Dominik. 2007. Wuala - A Distributed File System. ''Computer Engineering and Networks Laboratory, ETH Zurich. http://www.youtube.com/watch?v=3xKZ4KGkQY8</ref>.

	This fragmented structure is used by Wuala to ensure fast access in unusual circumstances as well. If a single storage node contains a fragment that suddenly becomes in high demand the storage node can redirect requests to other clients that recently downloaded that fragment. This ensures the system scales to high demand for a single file and is similar to other peer-to-peer systems.		This fragmented structure is used by Wuala to ensure fast access in unusual circumstances as well. If a single storage node contains a fragment that suddenly becomes in high demand the storage node can redirect requests to other clients that recently downloaded that fragment. This ensures the system scales to high demand for a single file and is similar to other peer-to-peer systems.

Lmundt: /* Overview */

2011-03-09T13:51:01Z

Overview

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	Wuala provides private user storage but it also provides a fairly rich infrastructure for sharing files. Users can have three levels that they can share files on, individuals, groups and public. These permissions are stored as metadata along with the data it represents.		Wuala provides private user storage but it also provides a fairly rich infrastructure for sharing files. Users can have three levels that they can share files on, individuals, groups and public. These permissions are stored as metadata along with the data it represents.

	Clients both put and get files from the Wuala cloud ( network ). The cloud itself can be conceived as being composed of client, storage and super nodes<ref> Gromilund Dominik. 2007. Wuala - A Distributed File System. ''Computer Engineering and Networks Laboratory, ETH Zurich. http://www.youtube.com/watch?v=3xKZ4KGkQY8</ref>. In this oversimplified view super nodes are responsible for the routing of requests, storage nodes are responsible for storing the files and clients are only responsible for consumption.		Clients both put and get files from the Wuala cloud ( network ). The cloud itself can be conceived as being composed of client, storage and super nodes<ref name="video"> Gromilund Dominik. 2007. Wuala - A Distributed File System. ''Computer Engineering and Networks Laboratory, ETH Zurich. http://www.youtube.com/watch?v=3xKZ4KGkQY8</ref>. In this oversimplified view super nodes are responsible for the routing of requests, storage nodes are responsible for storing the files and clients are only responsible for consumption.

	Increasing in detail: in Wuala all stored files are broken into fragments for speed and reliability. These fragments are stored on a number of storage nodes requiring significant routing solutions to provide quick lookup for storage and retrieval.		Increasing in detail: in Wuala all stored files are broken into fragments for speed and reliability. These fragments are stored on a number of storage nodes requiring significant routing solutions to provide quick lookup for storage and retrieval.

Lmundt: /* References */

2011-03-09T13:49:39Z

References

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	</references>		</references>

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