Why a PKCS#12 file could not be read or written.

PKCS12.decode/3 and PKCS12.encode/3 return it as {:error, %PKCS12.Error{}}, and PKCS12.decode!/3 and PKCS12.encode!/3 raise it. Match on :reason:

• :malformed - not a valid PKCS#12 structure.
• :invalid_password - the MAC does not match, or, in a file without a MAC, the content does not decrypt.
• {:unsupported_version, version} - the PFX version is not 3.
• {:unsupported_algorithm, oid} - an algorithm the library does not implement, with its OID in dotted form.

• {:unsupported, :public_key_integrity | :public_key_privacy} - the file is signed with, or encrypted to, a public key instead of a password. Such files are very rare.

• {:not_available, algorithm} - the library knows the algorithm, but the :crypto application of this system (its OpenSSL) refuses it. For example, RC4 when the OpenSSL "legacy" provider is missing, or parameters that a FIPS provider rejects.
• {:too_many_iterations, count} - one key derivation asks for more iterations than the :max_iterations option allows.
• {:too_many_total_iterations, count} - the work of all derivations together goes beyond the :max_total_iterations option; count is the work done or due when the limit was reached.
• {:unsupported_mac_key_size, bytes} - a PBMAC1 key size outside 20..64 bytes.
• {:invalid_input, field} - when writing, field (:private_key, :certificate or :ca_certificates) is not a key or certificates in a form that PKCS12.encode/3 takes.

The error never carries the password or any key material.