Class: OpenLoam::Encryption::HkdfKeyProvider

Inherits:
KeyProvider
  • Object
show all
Defined in:
lib/open_loam/encryption/key_provider.rb

Overview

Default provider: derive a per-scope, per-purpose key from one master key with HKDF-SHA256. Deterministic, so no key needs to be stored, and one scope's key can NEVER equal another's because the scope is bound into the HKDF info. Purpose separation means the encryption key and the blind-index (HMAC) key derived for one scope are independent.

Constant Summary collapse

SALT =

A fixed, non-secret salt. HKDF's strength comes from the master key's entropy; the salt only has to be stable so derivation is reproducible.

"loam.encryption.hkdf.v1".freeze
KEY_BYTES =

AES-256 and HMAC-SHA256 both take a 32-byte key

32

Instance Method Summary collapse

Instance Method Details

#data_key(scope:, purpose:) ⇒ Object 



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# File 'lib/open_loam/encryption/key_provider.rb', line 28

def data_key(scope:, purpose:)
  derive(scope, purpose, OpenLoam::Encryption.master_key)
end

#previous_data_key(scope:, purpose:) ⇒ Object

The same derivation under the key being rotated away from, so decryption can fall back to it while open_loam:encryption:rotate rewrites rows under the new one. nil when no previous key is configured.



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# File 'lib/open_loam/encryption/key_provider.rb', line 35

def previous_data_key(scope:, purpose:)
  previous = OpenLoam::Encryption.previous_master_key
  return nil if previous.nil?

  derive(scope, purpose, previous)
end