Card-Host Secure Channel Initiation Without Key Identifier Exposure
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Solution Overview
Problem
Existing secure channel initiation protocols between a card and a host, such as those described in GPC_SPE_014, expose confidential data like key version numbers and identifiers, which can be leaked to unauthorized entities, compromising security.
Innovation Solution
A secure channel initiation procedure where the card and host use a static encryption key, generate unique session keys, and replace key version numbers and identifiers with an anonymous SCP key identity, processed through cryptographic functions, ensuring secure communication without exposing sensitive information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If key version number and key identifier are transmitted in the INITIALIZE UPDATE command, then the host can verify the card's static encryption key, but confidential key information may be leaked to unauthorized entities
Solution Approach 1:
The patent introduces an intermediary mechanism (cryptographic processing of key version and identifier with the static encryption key) that transforms sensitive key information into a secure intermediate form (SCP key identity) for transmission. This intermediary step allows the host to verify the card's identity without exposing the actual key version number and identifier, thus resolving the contradiction between verification reliability and information leakage prevention
Solution Approach 2:
The patent creates a cryptographic copy (SCP key identity) of the key version number and identifier that can be transmitted safely. Instead of sending the actual sensitive values, the system sends a derived cryptographic representation that maintains verification functionality while eliminating the security risk of direct exposure. This copying approach allows the host to perform verification using the derived values without ever handling the sensitive original data
2Object-affected harmful factors
If key version number and key identifier are concealed using cryptographic functions, then key information security is improved, but the complexity of the initialization process increases
Solution Approach 1:
The patent makes the static encryption key serve multiple functions: it is used both for generating the session key (cryptographic function with host challenge and card challenge) and for deriving the SCP key identity (cryptographic processing of key version and identifier). This multi-functionality reduces overall system complexity by eliminating the need for separate mechanisms to handle key derivation and identity generation, thus offsetting the added complexity of cryptographic processing
Data Source
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AI summary
A procedure for initiating a secure communication session between a card and a host, a static encryption key being assigned to the card and stored in the card, each of the card and the host providing of a key version number and a key identifier of said static key, the procedure comprising steps at the card: - receive, from the host, an INITIALIZE UPDATE command comprising a host challenge, which is a value unique to the session; - generate a card challenge, which is a value unique to the session, herein processing at least the card's static encryption key, key diversification data and a sequence counter with a first cryptographic function; - generate a session key (S-ENC), herein processing the card's static encryption key, the host challenge and the card challenge with a second cryptographic function; - calculate a card cryptogram using the session key (S-ENC); - send to the host an INITIALIZE UPDATE reply in which the card cryptogram, the sequence counter and the card challenge are comprised, to enable the host to verify the card cryptogram; characterized in that: - each of the card and the host provide of an SCP key identity associated with said key version number and said key identifier of the card's static encryption key; - the INITIALIZE UPDATE command comprises the SCP key identity, and doesn't comprise said key version number and said key identifier; - to generate the card challenge, in addition said key version number and said key identifier are processed with the first cryptographic function.