Nikolaos Living Triandopoulos

US Patent:

8572385, Oct 29, 2013

Filed:

Jul 29, 2011

Appl. No.:

13/194702

Inventors:

Roberto Tamassia - Providence RI, US
Nikolaos Triandopoulos - Arlington MA, US

Assignee:

Brown University - Providence RI
Boston University - Boston MA

International Classification:

H04L 9/32

US Classification:

713171

Abstract:

A system and method for cryptographically checking the correctness of outsourced set operations performed by an untrusted server over a dynamic collection of sets that are owned (and updated) by a trusted source is disclosed. The system and method provides new authentication mechanisms that allow any entity to publicly verify a proof attesting the correctness of primitive set operations such as intersection, union, subset and set difference. Based on a novel extension of the security properties of bilinear-map accumulators as well as on a primitive called accumulation tree, the system and method achieves optimal verification and proof complexity, as well as optimal update complexity, while incurring no extra asymptotic space overhead. The method provides an efficient proof construction, adding a logarithmic overhead to the computation of the answer of a set-operation query. Applications of interest include efficient verification of keyword search and database queries.

US Patent:

20100110935, May 6, 2010

Filed:

Jan 24, 2007

Appl. No.:

12/223224

Inventors:

Roberto Tamassia - Providence RI, US
Nikolaos Triandopoulos - Cambridge MA, US

Assignee:

BROWN UNIVERSITY - Providence RI

International Classification:

H04L 12/28
G06F 17/30

US Classification:

370256, 707770, 707E17032

Abstract:

A method and distributed network are provided. The method includes: providing an abstract tree structure having a root node, a plurality of tree nodes, and a plurality of leaf nodes, wherein each leaf node corresponds to at least a portion of data (box ); mapping, in accordance with a first mapping function, a plurality of first network nodes of a distributed network to the plurality of tree nodes of the abstract tree structure (box ); mapping, in accordance with a second mapping function, a plurality of second network nodes of the distributed network to the plurality of leaf nodes of the abstract tree structure (box ); assigning a unique identifier to the root node, each tree node, and each leaf node (box ); storing, at each first network node, the unique identifier of the corresponding tree node, the unique identifier of a parent of that tree node, and the unique identifiers of children of that tree node (box ); storing, at each second network node, the corresponding at least a portion of data and path information having a path of nodes from the corresponding leaf node to the root node (box ); providing a distributed hash tree corresponding to the abstract tree structure, wherein the distributed hash tree includes a corresponding hash value for each node of the abstract tree structure, wherein the corresponding hash value for the root node is atop hash value (box ); signing the top hash value of the distributed hash tree (box ); and storing, at each second network node, the corresponding hash value of the corresponding tree node and the corresponding hash values of children of that tree node (box ).

US Patent:

20110225429, Sep 15, 2011

Filed:

Aug 28, 2009

Appl. No.:

12/737887

Inventors:

Roberto Tamassia - Providence RI, US
Nikolaos Triandopoulos - Arlington MA, US

International Classification:

G06F 21/00

US Classification:

713189

Abstract:

In one exemplary embodiment, an apparatus includes a memory storing data and a processor performing operations. The apparatus generates or maintains an accumulation tree for the stored data—an ordered tree structure with a root node, leaf nodes and internal nodes. Each leaf node corresponds to a portion of the data. A depth of the tree remains constant. A bound on a degree of each internal node is a function of a number of leaf nodes of a subtree rooted at the internal node. Each node of the tree has an accumulation value. Accumulation values of the root and internal nodes are determined by hierarchically employing an accumulator over the accumulation values of the nodes lying one level below the node in question. The accumulation value of the root node is a digest for the tree.

US Patent:

20190182232, Jun 13, 2019

Filed:

Aug 17, 2018

Appl. No.:

16/104280

Inventors:

- Hopkinton MA, US
Nikolaos Triandopoulos - Arlington MA, US
John Brainard - Sudbury MA, US

International Classification:

H04L 29/06
G06F 21/31

Abstract:

Techniques are provided for implementing predefined access policies based on auxiliary information embedded in one-time passcode authentication tokens. An exemplary method comprises receiving an authentication passcode generated by a token of a user, wherein the received authentication passcode is derived from a secret seed and based on at least one protocode and embedded auxiliary information; processing the received authentication passcode to extract the embedded auxiliary information from the received authentication passcode, wherein the embedded auxiliary information comprises (i) a silent alarm signal indicating a potential compromise of the token, and (ii) a drifting key signal indicating a current drifting key state of the token, wherein the drifting key signal is processed to detect a cloning of the token; and implementing a predefined access policy (e.g., replace or disable the token of one or more users) based on respective values of the silent alarm signal and the drifting key signal.

US Patent:

20150242616, Aug 27, 2015

Filed:

Feb 26, 2014

Appl. No.:

14/190195

Inventors:

Alina Oprea - Arlington MA, US
Kevin D. Bowers - Melrose MA, US
Nikolaos Triandopoulos - Arlington MA, US
Ting-Fang Yen - Cambridge MA, US
Ari Juels - Brookline MA, US

International Classification:

G06F 21/44

Abstract:

There is disclosed a method for use in credential recovery. In one exemplary embodiment, the method comprises determining a policy that requires at least one trusted entity to verify the identity of a first entity in order to facilitate credential recovery. The method also comprises receiving at least one communication that confirms verification of the identity of the first entity by at least one trusted entity. The method further comprises permitting credential recovery based on the received verification.

US Patent:

20140245006, Aug 28, 2014

Filed:

Feb 26, 2014

Appl. No.:

14/190642

Inventors:

- Providence RI, US
Roberto Tamassia - Providence RI, US
Nikolaos Triandopoulos - Cambridge MA, US

Assignee:

Brown University - Providence RI

International Classification:

G06F 21/64
G06F 17/30

US Classification:

713168, 713189

Abstract:

In one exemplary embodiment, an apparatus includes a memory storing data and a processor performing operations. The apparatus generates or maintains an accumulation tree for the stored data—an ordered tree structure with a root node, leaf nodes and internal nodes. Each leaf node corresponds to a portion of the data. A depth of the tree remains constant. A bound on a degree of each internal node is a function of a number of leaf nodes of a subtree rooted at the internal node. Each node of the tree has an accumulation value. Accumulation values of the root and internal nodes are determined by hierarchically employing an accumulator over the accumulation values of the nodes lying one level below the node in question. The accumulation value of the root node is a digest for the tree.