Anonymous and Non-transferable Biometric Digital ID on Blockchain

Abstract

The first user centric Identity Management system on the Bitcoin Blockchain was introduced in 2017 by Augot et al. However, Bitcoin is not an anonymous cryptocurrency, therefore, privacy is not guaranteed. Hence, one aspect of the identity, namely biometrics should be processed in a privacy preserving manner and as encrypted. This way, non-transferability is guaranteed in addition to the anonymous processing of the most important personal identifier, namely sensitive biometric data. In fact, the first anonymous biometric identification system that guarantees these notions was described in 2018 on top of Zerocoin protocol. In this system, biometric data (fingerprint,face, iris), are stored as encrypted on the Blockchain. If there is an incoming identification request from the user to access a service, the biometric matching is performed by the nodes/miners in the encrypted domain and if a match is found, it is recorded on the Blockchain. In summary, through anonymous transfers, service providers complete the anonymous biometric identification procedure and provides the necessary access to the service. In this research article, we evalute recent privacy coins of Zerocash and Monero in addition to Zerocoin, and examine whether there exists better solutions in biometric based Identity Management systems with respect to efficiency and privacy. First, we describe anonymous biometric identification/authentication systems based on anonymous cryptocurrencies and then we modify them slightly to obtain anonymous Digital ID. Finally, we compare the analyzed privacy coins in order to find the cheapest solution. Initial results show that Cryptonote based Monero provides the most ideal system, leading to the evaluation of RingCT based systems guaranteeing a higher security level.

Keywords

• Blockchain
• Biometrics
• Privacy
• Anonymity
• Digital ID
• Bitcoin
• Zerocoin
• Zerocash
• Monero

Blokzincirde Anonim ve Devredilemez Biyometrik Dijital Kimlik

Öz

2017 yılında Augot et al. tarafından Bitcoin Blokzinciri üzerinde ilk kullanıcı odaklı Kimlik Yönetimi sistemi tanımlanmıştır. Ancak Bitcoin kripto para birimi anonim değildir, dolayısıyla mahremiyeti saglamamaktadır. Bu nedenle, kimliği oluşturan unsurlardan biri olan biyometrik verilerin mahremiyeti sağlayan bir platformda ve şifreli olarak yönetilmesi gereklidir. Böylelikle hem devredilemezlik özelliği sağlanmış olacak, hem de kişisel verilerin en başında gelen hassas biyometrik veriler kriptografik yöntemler ile korunarak, anonim şekilde işlem görücektir. Esasen, bu özellikleri sağlayan ilk anonim biyometrik tanımlama sistemi, 2018 yılında Zerocoin blokzinciri üzerinde tasarlanmıştır. Bu sistemde biyometrik veriler (parmak izi, yüz, iris) şifreli olarak blokzincirde tutulmakta, kullanıcıdan bir servise erişim amaclı kimlik tanımlama talebi geldiğinde, biyometrik tanımlama madenciler tarafından şifreli alanda yapılmakta ve bir eşleşme bulunduğunda sonuç blokzincire kayıt edilir. Özetle, anonim transferler ile, servis saglayıcılar anonim biyometrik tanımlama işlemini tamamlayarak kullanıcının talep ettiği erişim iznini sağlarlar. Bu araştırma makalesinde, Zerocoin ile birlikte güncel diğer anonim kripto para birimleri olan Zerocash ve Monero analiz edilerek, biyometrik verilere dayalı dijital kimlik yönetim sistemlerinde performans ve mahremiyet açısından daha iyi çözümlerin mevcut olup olmadığı incelenecektir. Bu inceleme sırasında önce anonim kriptoparalara ait blokzincirler üzerinde biyometrik tanımlama uygulaması, akabinde bu uygulama üzerinde basit bir modifikasyon ile anonim dijital kimlik yönetimi sistemi elde edilecektir. Son olarak bu çözümlerden en az maliyetli olanı, analiz edilen anonim kripto para sistemleri karşılaştırılarak tespit edilecektir. İlk sonuçlara göre, Cryptonote tabanlı Monero en uygun sistem olup, gelecekte daha yüksek güvenlik sağlayan RingCT tabanlı sistemler de değerlendirilecektir.

Anahtar Kelimeler

• Blokzincir
• Biyometri
• Mahremiyet
• Anonimlik
• Dijital Kimlik
• Bitcoin
• Zerocoin
• Zerocash
• Monero

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