The goal of the utils is to provide high-level components which can perform certain complex operations found in OEMCrypto, with the intention to be used in the testbed code and unittests. The most important aspect of this is to avoid providing any implementation-specific utilities here.

Practical exceptions to goal

The use of C++
- Techincally specific to a specific implementation
- Our testbed and test code both use C++, and this is intended to be used by these systems
Raw data formats
- Generally, we use std::string, std::vector<uint8_t> and uint8_t* to store and manipulate bytes of data
Reasonable resource limitations
- Theoretical algorithms to usually take into consideration computer resources, but real implementations are still subjected to them
- Ex. max buffer size which component operate on
Use of Widevine's logging system

Example of goal-aligned components

Standard cryptographic operations wrappers
- Schemes, protocols and algorithms which are publicly published
- Mechanically similar to other cryptographical software libraries
OEMCrypto-specific RSA and ECC cryptographic operations
- OEMCrypto has a small set of protocols based on RSA and ECC cryptography
- These protocols are well-defined by the OEMCrypto specification, and any implementation would need to include an implementation of these exact protocols
DRM key cryptographic operations
- Built upon RSA and ECC operations
- Only performs DRM key operations which ANY implementation would also have to perform in the same way

Example of hypothetical anti-goal components

DRM key wrapping algorithms
- The OEMCrypto specification (as of v19) does not specify exactly how wrapping a DRM key is to be performed.
- Although many OEMs likely use the same implementaion as the reference, it is still an undefined operation.
- Note: Standard parts of a wrapping algorithm (such as AES encryption) may be provided.
Usage Table Header/Entry encryptors
- Similar to DRM key wrapping, the OEMCrypto specification (as of v19) does not specify exactly how the Usage Table's header and entries are to be encrypted and signed
Key handle to session ID serialization
- This is NOT defined by the OEMCrypto specification

Current Components

This is a non-exhausted list of components found within this library which provided general OEMCrypto operations.

EccPublicKey and EccPrivateKey
- High-level wrappers around OEMCrypto-specific protocols of Elliptic Curve Cryptography
- Generally aimed for how ECC-based DRM keys are used, as well as for a small set of BCC operations
RsaPublicKey and RsaPrivateKey
- High-level wrappers around OEMCrypto-specific protocols of RSA Cryptography
- Generally aimed for how RSA-based DRM and OEM Cert keys are used, as well as a small set of Cast-specific operations
DrmPrivateKey
- A high-level wrapper around OEMCrypto's DRM key
- Provides a generic DRM key interface, which internally handles the different cases of using either a RSA or ECC based DRM key
wvcrc32.h
- Set of functions for OEMCrypto's CRC-32 algorithm
  - CRC-32 is a general term for 32-bit Cyclic Redundancy Checks
  - OEMCrypto has a well-defined set of parameters which all implementers must use to work with Widevine's software stack
hmac.h and cmac.h
- HMAC and CMAC C++ wrappers, restricted to only the algorithm parameters which are used within OEMCrypto
KeyDeriver
- High-level wrapper around OEMCrypto's key derivation algorithm
- Intended to be used only for messaging key derivation, which is well-defined within the OEMCrypto standard
- Note: Although the testbed uses this for other types of keys, the methods provided by KeyDeriver are only designed with messaging keys in mind.
CborValidator and specialized validators
- High-level validator for CBOR messages found within the Provisioning 4.0 protocol.
- Note: Although the error messages provided by this library are not defined the primary function of these components do follow the specification, and the error messages are used to inform a human user, not another software system.