Support every kind of operation expected from a full-blown crypto provider in decreasing order of priority:

1. ASN.1 (low-level abstractions, parsing, encoding, construction, high-level encoding) in the crypto context (i.e. no ANS.1 REAL, etc.)
2. Signing+Verifying
   • EC (NIST curves)
   • RSA (PKCS#1, PSS)
3. HW-backed crypto on iOS + Android
   • Biometric Auth
   • Passphrase-based Auth
   • Attestation support
4. Symmetric Encryption/Decryption
   • AES-CBC
   • AES-GCM
5. Key Agreement
   • ECDH
6. Asymmetric Encryption/Decryption
   • RSA
7. Key Wrapping
   • AES key wrapping
8. KDF/KSF
   • HKDF
   • PBKDF2
   • Scrypt
9. MAC
   • HMAC-SHA1
   • HMAC-SHA{256-512}

This is not about supporting specific algorithms, paddings, etc, but to have all interfaces ready, with at least a single algorithm being usable across all targets