Technical Presentation
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System Rationale
System Architecture
Secure Channel Establishment
◦ Username/Password
◦ Cartão Cidadão
◦ Digital Certificate
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Secure Functionalities
◦ Competence Verification
◦ Document Signature and Validation
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System Security Analysis
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Client asked for a system who was able to:
◦ Verify a title or competency of a subject;
◦ Digitally Sign a document with a given Competency
of a subject.
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All the communication and processes
performed in a secure fashion
CERTCOP was developed to address these
(and more…) requisites
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3 Modes Used:
◦ Username/Password
◦ Cartão Cidadão
◦ Digital Certificates
 Used with a slight modification in Web Server
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All modes based on EKE (Encrypted Key
Exchange)
At the end each entity has:
◦ Public/Private Key;
◦ Symmetric Session Key;
◦ Mutual Authentication Guarantees.
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One signature is generated for every message
𝑀𝑒𝑠𝑠𝑎𝑔𝑒𝑆𝑖𝑔𝑛𝑎𝑡𝑢𝑟𝑒(𝑈𝑠𝑒𝑟𝐼𝑑, 𝑅𝑒𝑚𝑜𝑡𝑒𝑈𝑠𝑒𝑟𝐼𝑑, 𝐶𝑢𝑟𝑟𝑒𝑛𝑡𝑇𝑆, 𝑀𝑒𝑠𝑠𝑎𝑔𝑒𝐻𝑎𝑠ℎ, {𝐻𝑎𝑠ℎ 𝑀𝑒𝑠𝑠𝑎𝑔𝑒𝑆𝑖𝑔𝑛𝑎𝑡𝑢𝑟𝑒) 𝐾 − )
◦ Provides Integrity, Freshness and Non-Repudiation
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The original message, along with the
Signature, is ciphered with the Symmetric
Session Key
◦ Providing Confidentiality and Authentication
𝑆𝑒𝑐𝑢𝑟𝑒𝑀𝑒𝑠𝑠𝑎𝑔𝑒( 𝑂𝑟𝑖𝑔𝑖𝑛𝑎𝑙𝑀𝑒𝑠𝑠𝑎𝑔𝑒, 𝑀𝑒𝑠𝑠𝑎𝑔𝑒𝑆𝑖𝑔𝑛𝑎𝑡𝑢𝑟𝑒 𝐾𝑠 )
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Competence Verification
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Document Signature and Validation
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𝐺𝑒𝑛𝑆𝑖𝑔𝑛𝑎𝑡𝑢𝑟𝑒( 𝐻𝑎𝑠ℎ 𝑁𝑜𝑢𝑛𝑐𝑒, 𝐶𝑜𝑚𝑝𝑒𝑡𝑒𝑛𝑐𝑦 𝐾𝐶𝑖𝑡𝑖𝑧𝑒𝑛𝐶𝑎𝑟𝑑
)
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𝐴𝑢𝑡ℎ𝑆𝑖𝑔𝑛𝑎𝑡𝑢𝑟𝑒( 𝐻𝑎𝑠ℎ 𝑁𝑜𝑢𝑛𝑐𝑒, 𝐶𝑜𝑚𝑝𝑒𝑡𝑒𝑛𝑐𝑦 𝐾𝐶𝑖𝑡𝑖𝑧𝑒𝑛𝐶𝑎𝑟𝑑
)
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To each signed document is generated the
following signature:
𝐷𝑜𝑐𝑢𝑚𝑒𝑛𝑡𝑆𝑖𝑔𝑛𝑎𝑡𝑢𝑟𝑒(𝐻𝑎𝑠ℎ 𝐷𝑜𝑐𝑢𝑚𝑒𝑛𝑡 , 𝑆𝑒𝑟𝑖𝑎𝑙𝑁𝑢𝑚𝑏𝑒𝑟, 𝑈𝑠𝑒𝑟𝐼𝑑, 𝑈𝑠𝑒𝑟𝐶𝑜𝑚𝑝𝑒𝑡𝑒𝑛𝑐𝑒,
𝑆𝑒𝑟𝑖𝑎𝑙𝑁𝑢𝑚𝑏𝑒𝑟𝑆𝑖𝑔𝑛𝑒𝑟𝐶𝑒𝑟𝑡𝑖𝑓𝑖𝑐𝑎𝑡𝑒 𝑉𝐸𝑅𝐼𝐶𝑂𝑃? , 𝑆𝑖𝑔𝑛𝑎𝑡𝑢𝑟𝑒𝑉𝑎𝑙𝑖𝑑𝑖𝑡𝑦, 𝑆𝑖𝑔𝑛𝑎𝑡𝑢𝑟𝑒𝐺𝑒𝑛𝑒𝑟𝑎𝑡𝑖𝑜𝑛𝐷𝑎𝑡𝑒,
−
{𝐻𝑎𝑠ℎ(𝐷𝑜𝑐𝑢𝑚𝑒𝑛𝑡𝑆𝑖𝑔𝑛𝑎𝑡𝑢𝑟𝑒)}𝐾𝐶𝐸𝑅𝑇𝐶𝑂𝑃
)
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If the Document has a higher priority it is
stored and verified by another system
◦ VERICOP
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This additional service can be billed at a
higher price
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State of the art cryptographic algorithms and
protocols used:
◦ AES (with 128 bits key and 10 encryption rounds)
◦ SHA-2 (256 bits)
◦ RSA (with 2048 bits key for certificate, 1024 for the
transient key pairs)
◦ Adapted EKE Protocol
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Quite few practical attacks reported on those
algorithms
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System Security is an important issue:
◦ Database Servers Isolation
◦ Credentials Management
◦ Firewall Configuration
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Users and Administrators security awareness
is vital to the Security
◦ Neither Users nor Administrators should ever
release their passwords to anybody
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Web Interface will be available in a future
release;
System design based on state of the art
security technologies
◦ Great overall System Security Level
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Special care must be taken to the
maintenance and operation procedures of the
system
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