Encode
Agree on the model.
Participating organisations establish a shared basis upfront. Training data is encoded against this basis: structure is captured as coefficients, the unpredictable part as the residual. Both are treated as private.

Transmit
Only residuals train the model
Raw datasets stay on-site. Organisations exchange tokens, not raw records, and the coefficient features feed training directly.

Reconstruct
Exact data when authorised
The basis is regenerated locally. Raw training examples can be recovered exactly when access is granted, for validation, auditing, or retraining.