PPK v3 Adoption Decision: Keep v2 Compatibility or Upgrade for Stronger Protection

Goal: Determine whether to convert existing PPK v2 private keys to the newer PPK v3 format to benefit from Argon2‑based passphrase derivation while preserving usability across older PuTTY releases and third‑party tools that may not recognize v3.

Constraints: PuTTYgen versions after 0.71 default to v3 for newly generated keys, but older PuTTY and many external parsers cannot read v3 and may fail silently; there is no automatic migration path, so administrators must weigh stronger protection against possible interoperability breaks.

What are the practical risks of silent failures when a tool encounters a v3 key? How can an organization enforce a consistent key version across heterogeneous toolchains? Is there a recommended validation step before performing a bulk conversion of legacy keys?