struct ara::crypto::SecureCounter

The structure ara::crypto::SecureCounter serves in module crypto as a 128-bit secure counter consisting of two 64-bit integers for the least significant bits ([SWS_CRYPT_30002]) and the most significant bits ([SWS_CRYPT_30003]). Calling components use this data type to represent robust counter values, whereby incrementations and carry logics between the subwords must be controlled manually. As a pure value type, the structure provides no internal synchronization, which is why concurrent accesses in multithreading environments must strictly be coordinated externally.

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Context

The structure ara::crypto::SecureCounter functions within module crypto of the AUTOSAR Adaptive Platform as a fundamental data type for representing a 128-bit wide cryptographic counter. Defined in the header file ara/crypto/common/base_id_types.h, the data structure is composed of two 64-bit integers of type std::uint64_t: the data element mLSQW for the least significant 64 bits according to [SWS_CRYPT_30002] and the data element mMSQW for the most significant 64 bits according to [SWS_CRYPT_30003]. In security architectures, counter values of this magnitude serve to ensure the temporal freshness of messages and effectively counter replay attacks. Interpretation: As a standardized data type, the structure is likely to serve primarily as an interface and storage format for monotonic counters or sequence numbers exchanged by cryptographic protocols, drivers, and hardware-oriented security components. Question Q-57197e2ecabd5cab (open) Since the specification declares ara::crypto::SecureCounter as a pure data container without direct algorithmic binding, higher-level layers interact directly with the two member components to check, persist, or embed counter values into protocol messages.

Lifecycle

As a classic C++ structure (struct), ara::crypto::SecureCounter is subject to a lightweight lifecycle without dynamic memory management or stateful management logic. Instantiation usually takes place directly on the stack as a local value type or embedded as a field element in higher-level contexts such as security event headers or cryptographic session descriptors. As a simple data container, the structure presumably exhibits regular C++ value semantics with implicit copy and assignment behavior, but provides no internal synchronization mechanisms for concurrent access. Question Q-a4d95542ea77870d (open) For developers, this means that simultaneous read and write accesses from different threads must be protected by external synchronization primitives to prevent data inconsistencies during counter updates. The lifecycle of an instance ends automatically upon leaving the respective scope, with no explicit releases or cleanups being necessary.

Usage Path

The typical usage path comprises initialization, step-by-step incrementation, and reading of the combined 128-bit counter value via the two structural components. A caller first instantiates the structure and assigns the initial counter values to the low-order subword mLSQW ([SWS_CRYPT_30002]) and the high-order subword mMSQW ([SWS_CRYPT_30003]). During continuous counting operations, primarily the low-order word mLSQW is incremented. When mLSQW reaches the maximum value of the 64-bit range, a computational carry-over occurs to the high-order word mMSQW, which is increased by one. Interpretation: Arithmetic operations such as incrementation and carry handling are likely to be implemented on the caller side, since the specification declares no member functions of its own for ara::crypto::SecureCounter. Question Q-68babc70b53a5745 (open) During transmission or persistence, the two 64-bit members are serialized in a structured manner, whereby attention must be paid to consistent byte and word order in order to preclude misinterpretations of the overall value on the receiver side.

Error Scenarios

Since ara::crypto::SecureCounter represents a pure data structure without member functions of its own, the structure neither throws exceptions nor returns error specifications or error codes of type ara::core::ErrorCode during operations. Consequently, error scenarios do not arise within the structure itself, but through incorrect handling of the two subwords in the calling software layers. A critical error scenario is an unnoticed arithmetic overflow of the overall counter when both mLSQW ([SWS_CRYPT_30002]) and mMSQW ([SWS_CRYPT_30003]) exhaust their maximum value range and wrap around to zero, which can lead to security vulnerabilities in replay protection mechanisms. Further pre- and postcondition violations occur if the carry from mLSQW to mMSQW is missed during updates, or if undefined memory values enter calculations due to incomplete initialization. Calling components must therefore ensure prior to further processing that both data elements are initialized consistently and that carry logics are implemented correctly.