Add kdf module: Key Derivation Function API (JEP 510, final in JDK 25), HKDF, RFC 5869 vectors, interop with Python cryptography and openssl, per-tenant keys

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_017ic4b7rnC7jppGGdHGESvy

kdf/output/06-tenants.txt

@@ -0,0 +1,18 @@
+$ java -cp classes Tenants      (25.0.5+8-LTS)
+== Per-tenant, per-purpose, per-version keys (first 8 bytes shown)
+tenant-acme  aes v1 = 503b6a158de948ef   hmac v1 = de11af197467596c   aes v2 = 0c80331430e74d8d
+tenant-globex  aes v1 = 3e7dd7c93250c77e   hmac v1 = ab1c9c0b01b4e64b   aes v2 = 22859d1db92cf04b
+PASS  same inputs give the same key every time (nothing to store)
+PASS  two tenants get different keys
+PASS  encryption key and MAC key of one tenant differ
+PASS  key version 2 differs from version 1 (rotation)
+== Isolation in practice: tenant A's ciphertext is opaque to tenant B's key
+acme key  decrypts: invoice #4711 for acme
+globex key fails:   AEADBadTagException: Tag mismatch
+PASS  tenant B cannot open tenant A's data
+== HMAC key from the same master, used for a signed token
+tag = 3cb1fb88afc1c173475dac3a12f68f05...
+== The info bytes that separate the contexts (hex) for tenant-acme / aes-gcm / v1
+000f61636d652d62696c6c696e672f763100076165732d67636d000b74656e616e742d61636d65000400000001
+ALL CHECKS PASSED
+exit=0