Hello @michaelb - it is certainly feasible to add cryptographic providers to SQLCipher. This basically involves writing a shim for the provider to call all the appropriate functions. Here is an example written for NSS:
sqlcipher/crypto_nss.c at master · sqlcipher/sqlcipher (github.com)
Once that is in place, you can programmatically change the provider. In order to extend it to be a default provider, you’d need to implement additional changes in a few other files and the build chain.
That said, we haven’t really considered adding BearSSL as a provider, since we already support a fairly large number with OpenSSL, CommonCrypto, NSS, and LibTomCrypt. Thus we haven’t seen a compelling reason incorporate others like BearSSL. Is there a specific reason one of the other providers wouldn’t work for you?