Please see the paper at https://eprint.iacr.org/2021/968 (title and abstract below, I am a co-author) for a novel way of implementing signatures in a white-box setting.
White-Box Implementations for Hash-Based Signatures and One-Time Passwords
Abstract: White-box cryptography aims at providing protection against a powerful adversary which is in complete control of the execution environment of the cryptographic operation. Most existing white-box implementations focus on symmetric encryption. In particular, we are not aware of any previous work on general-purpose digital signature schemes secure against white-box attackers. We present white-box implementations for hash-based signatures so that the security against white-box attackers depends not on the availability of a white-box secure pseudorandom function (in addition to a general one-way function). We also present a hash tree-based solution for one-time passwords secure in a white-box attacker context.