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Papers by Birgit Pfitzmann

Research paper thumbnail of A Remark on a Signature Scheme Where Forgery can be Proved

Lecture Notes in Computer Science, 1991

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Research paper thumbnail of Error- and Collusion-Secure Fingerprinting for Digital Data

Lecture Notes in Computer Science, 2000

Fingerprinting means making copies of the same data identifiable by hiding additional information... more Fingerprinting means making copies of the same data identifiable by hiding additional information (a fingerprint) in the data. Embedding the additional data can be done by watermarking techniques, which are mainly a branch of signal processing. Most watermarking methods, however, do not treat colluding adversaries who have obtained more than one copy, compare their copies, see differences and use this

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Research paper thumbnail of Federated Identity Management

Data-Centric Systems and Applications, 2007

ABSTRACT The more real business and interaction with public authorities is performed in digital f... more ABSTRACT The more real business and interaction with public authorities is performed in digital form, the more important the handling of identities over open networks becomes. The rise in identity theft as a result of the misuse of global but unprotected identifiers like credit card numbers is one strong indicator of this. Setting up individual passwords between a person and every organization he or she interacts with also offers very limited security in practice. Federated identity management addresses this critical issue. Classic proposals like Kerberos and PKIs never gained wide acceptance because of two problems: actual deployment to end users and privacy. We describe modern approaches that solve these problems. The first approach is browser-based protocols, where the user only needs a standard browser without special settings. We discuss the specific protocol types and security challenges of this protocol class, as well as what level of privacy can and cannot be achieved within this class. The second approach, private credentials, solves the problems that none of the prior solutions could solve, but requires the user to install some local software. Private credentials allow the user to reveal only the minimum information necessary to conduct transactions. In particular, it enables unlinkable transactions even for certified attributes. We sketch the cryptographic solutions and describe how optional properties such as revocability can be achieved, in particular in the idemix system.

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Research paper thumbnail of Non-Determinism in Multi-Party Computation (Abstract)

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Research paper thumbnail of The Dining Cryptographers in the Disco - Underconditional Sender and Recipient Untraceability with Computationally Secure Serviceability (Abstract)

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Research paper thumbnail of Properties of Payment Systems: General Definition Sketch and Classification

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Research paper thumbnail of A Composable Cryptographic Library with Nested Operations (Extended Abstract)

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Research paper thumbnail of Information-Theoretic Pseudosignatures and Byzantine Agreement for t ≥ n/3

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Research paper thumbnail of Unconditional Byzantine Agreement for any Number of Faulty Processors — Extended Abstract

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Research paper thumbnail of Die PERSEUS System-Architektur

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Research paper thumbnail of Unbedingte Unbeobachtbarkeit mit kryprographischer Robustheit

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Research paper thumbnail of Fail-stop-Signaturen und ihre Anwendung

... Sicherheit konstruiert. Mit „konventionelles Signatursystem“ bezeichnen wir eines gemäß diese... more ... Sicherheit konstruiert. Mit „konventionelles Signatursystem“ bezeichnen wir eines gemäß dieser Definition (darunter fällt auch RSA mit Redundanzprädikat, nur isteben seine Sicherheit bisher nicht bewiesen). Insbesondere ...

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Research paper thumbnail of Fail-stop Signatures and their Application

... 9, Jeroen van de Graaf: Multiparty Computations Ensuring Privacy of Each Party's Inp... more ... 9, Jeroen van de Graaf: Multiparty Computations Ensuring Privacy of Each Party's Input and - Chaum, Damgard - 1988. ... 5, Breaking the Ong-Schnorr-Shamir Signature Scheme for Quadratic Number Fields - Estes, Adleman, et al. - 1986. ...

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Research paper thumbnail of On the Existence of Statistically Hiding Bit Commitment Schemes and Fail-Stop Signatures

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Research paper thumbnail of Migration to Multi-image Cloud Templates

2011 IEEE International Conference on Services Computing, 2011

ABSTRACT IT management costs increasingly dominate the overall IT costs. The main hope for reduci... more ABSTRACT IT management costs increasingly dominate the overall IT costs. The main hope for reducing them is to standardize software and processes, as this leads to economies of scale in the management services. A key vehicle by which enterprises hope to achieve this is cloud computing, and they start to show interest in clouds outside the initial sweet spot of development and test. As business applications typically contain multiple images with dependencies, one is starting to standardize on multi-image structures. Benefits are ease of deployment of the entire structure and consistent later management services for the business applications. Enterprises have huge investments in their existing busi- ness applications, e.g., their web design, special code, database schemas, and data. The promises of clouds can only be realized if a significant fraction of these existing applications can be migrated into the clouds. We therefore present analysis tech- niques for mapping existing IT environments to multi-image cloud templates. We propose multiple matching criteria, leading to tradeoffs between the number of matches and the migration overhead, and present efficient algorithms for these special graph matching problems. We also present results from analyzing an existing enterprise environment with about 1600 servers. Index Terms—IT services, management costs, migration, clouds, multi-image templates;

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Research paper thumbnail of Privacy in browser-based attribute exchange

Proceeding of the ACM workshop on Privacy in the Electronic Society - WPES '02, 2002

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Research paper thumbnail of Asymmetric fingerprinting for larger collusions

Proceedings of the 4th ACM conference on Computer and communications security - CCS '97, 1997

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Research paper thumbnail of Composition and integrity preservation of secure reactive systems

Proceedings of the 7th ACM conference on Computer and communications security - CCS '00, 2000

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Research paper thumbnail of Polynomial fairness and liveness

Proceedings 15th IEEE Computer Security Foundations Workshop. CSFW-15, 2002

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Research paper thumbnail of Proving a WS-Federation passive requestor profile

Proceedings of the 2004 workshop on Secure web service - SWS '04, 2004

Currently, influential industrial players are in the proces s of realizing identity federation, i... more Currently, influential industrial players are in the proces s of realizing identity federation, in particular the authenti cation of browser users across administrative domains. WS-Federation is a joint protocol framework for Web Services clients and browser clients. While browser-based federation protocols, including Microsoft Passport, OASIS SAML, and Liberty be- sides WS-Federation, are already widely deployed, their secu- rity is still unproven and has been challenged by several anal- yses. One reason is a lack of cryptographically precise pro- tocol definitions, which impedes explicit design for securi ty as well as proofs. Another reason is that the security proper- ties depend on the browser and even on the browser user. We rigorously formalize a strict instantiation of the current WS- Federation Passive Requestor Interop profile and make expli cit assumptions for its general use. On this basis, we prove that the protocol provides authenticity and secure channel estab- lishment in a realistic trust scenario. This constitutes th e first positive security result for a browser-based identity fede ration protocol.

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Research paper thumbnail of A Remark on a Signature Scheme Where Forgery can be Proved

Lecture Notes in Computer Science, 1991

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Research paper thumbnail of Error- and Collusion-Secure Fingerprinting for Digital Data

Lecture Notes in Computer Science, 2000

Fingerprinting means making copies of the same data identifiable by hiding additional information... more Fingerprinting means making copies of the same data identifiable by hiding additional information (a fingerprint) in the data. Embedding the additional data can be done by watermarking techniques, which are mainly a branch of signal processing. Most watermarking methods, however, do not treat colluding adversaries who have obtained more than one copy, compare their copies, see differences and use this

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Research paper thumbnail of Federated Identity Management

Data-Centric Systems and Applications, 2007

ABSTRACT The more real business and interaction with public authorities is performed in digital f... more ABSTRACT The more real business and interaction with public authorities is performed in digital form, the more important the handling of identities over open networks becomes. The rise in identity theft as a result of the misuse of global but unprotected identifiers like credit card numbers is one strong indicator of this. Setting up individual passwords between a person and every organization he or she interacts with also offers very limited security in practice. Federated identity management addresses this critical issue. Classic proposals like Kerberos and PKIs never gained wide acceptance because of two problems: actual deployment to end users and privacy. We describe modern approaches that solve these problems. The first approach is browser-based protocols, where the user only needs a standard browser without special settings. We discuss the specific protocol types and security challenges of this protocol class, as well as what level of privacy can and cannot be achieved within this class. The second approach, private credentials, solves the problems that none of the prior solutions could solve, but requires the user to install some local software. Private credentials allow the user to reveal only the minimum information necessary to conduct transactions. In particular, it enables unlinkable transactions even for certified attributes. We sketch the cryptographic solutions and describe how optional properties such as revocability can be achieved, in particular in the idemix system.

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Research paper thumbnail of Non-Determinism in Multi-Party Computation (Abstract)

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Research paper thumbnail of The Dining Cryptographers in the Disco - Underconditional Sender and Recipient Untraceability with Computationally Secure Serviceability (Abstract)

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Research paper thumbnail of Properties of Payment Systems: General Definition Sketch and Classification

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Research paper thumbnail of A Composable Cryptographic Library with Nested Operations (Extended Abstract)

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Research paper thumbnail of Information-Theoretic Pseudosignatures and Byzantine Agreement for t ≥ n/3

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Research paper thumbnail of Unconditional Byzantine Agreement for any Number of Faulty Processors — Extended Abstract

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Research paper thumbnail of Die PERSEUS System-Architektur

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Research paper thumbnail of Unbedingte Unbeobachtbarkeit mit kryprographischer Robustheit

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Fail-stop-Signaturen und ihre Anwendung

... Sicherheit konstruiert. Mit „konventionelles Signatursystem“ bezeichnen wir eines gemäß diese... more ... Sicherheit konstruiert. Mit „konventionelles Signatursystem“ bezeichnen wir eines gemäß dieser Definition (darunter fällt auch RSA mit Redundanzprädikat, nur isteben seine Sicherheit bisher nicht bewiesen). Insbesondere ...

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Research paper thumbnail of Fail-stop Signatures and their Application

... 9, Jeroen van de Graaf: Multiparty Computations Ensuring Privacy of Each Party's Inp... more ... 9, Jeroen van de Graaf: Multiparty Computations Ensuring Privacy of Each Party's Input and - Chaum, Damgard - 1988. ... 5, Breaking the Ong-Schnorr-Shamir Signature Scheme for Quadratic Number Fields - Estes, Adleman, et al. - 1986. ...

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Research paper thumbnail of On the Existence of Statistically Hiding Bit Commitment Schemes and Fail-Stop Signatures

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Migration to Multi-image Cloud Templates

2011 IEEE International Conference on Services Computing, 2011

ABSTRACT IT management costs increasingly dominate the overall IT costs. The main hope for reduci... more ABSTRACT IT management costs increasingly dominate the overall IT costs. The main hope for reducing them is to standardize software and processes, as this leads to economies of scale in the management services. A key vehicle by which enterprises hope to achieve this is cloud computing, and they start to show interest in clouds outside the initial sweet spot of development and test. As business applications typically contain multiple images with dependencies, one is starting to standardize on multi-image structures. Benefits are ease of deployment of the entire structure and consistent later management services for the business applications. Enterprises have huge investments in their existing busi- ness applications, e.g., their web design, special code, database schemas, and data. The promises of clouds can only be realized if a significant fraction of these existing applications can be migrated into the clouds. We therefore present analysis tech- niques for mapping existing IT environments to multi-image cloud templates. We propose multiple matching criteria, leading to tradeoffs between the number of matches and the migration overhead, and present efficient algorithms for these special graph matching problems. We also present results from analyzing an existing enterprise environment with about 1600 servers. Index Terms—IT services, management costs, migration, clouds, multi-image templates;

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Privacy in browser-based attribute exchange

Proceeding of the ACM workshop on Privacy in the Electronic Society - WPES '02, 2002

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Asymmetric fingerprinting for larger collusions

Proceedings of the 4th ACM conference on Computer and communications security - CCS '97, 1997

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Composition and integrity preservation of secure reactive systems

Proceedings of the 7th ACM conference on Computer and communications security - CCS '00, 2000

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Polynomial fairness and liveness

Proceedings 15th IEEE Computer Security Foundations Workshop. CSFW-15, 2002

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Proving a WS-Federation passive requestor profile

Proceedings of the 2004 workshop on Secure web service - SWS '04, 2004

Currently, influential industrial players are in the proces s of realizing identity federation, i... more Currently, influential industrial players are in the proces s of realizing identity federation, in particular the authenti cation of browser users across administrative domains. WS-Federation is a joint protocol framework for Web Services clients and browser clients. While browser-based federation protocols, including Microsoft Passport, OASIS SAML, and Liberty be- sides WS-Federation, are already widely deployed, their secu- rity is still unproven and has been challenged by several anal- yses. One reason is a lack of cryptographically precise pro- tocol definitions, which impedes explicit design for securi ty as well as proofs. Another reason is that the security proper- ties depend on the browser and even on the browser user. We rigorously formalize a strict instantiation of the current WS- Federation Passive Requestor Interop profile and make expli cit assumptions for its general use. On this basis, we prove that the protocol provides authenticity and secure channel estab- lishment in a realistic trust scenario. This constitutes th e first positive security result for a browser-based identity fede ration protocol.

Bookmarks Related papers MentionsView impact