feat: security fixes and improved test coverages

Security Fixes

  1. Blowfish2 destructor added (blowfish2.h, blowfish2.cc) — zeros PArray and Sboxes on destruction
  2. Secure memory zeroing (blowfish.cc, blowfish2.cc) — both destructors now use volatile pointer writes to prevent compiler elision
  3. Input validation (blowfish.cc, blowfish2.cc) — initialize() now throws std::invalid_argument for null key, empty key, or key > 56 bytes
  4. Copy assignment deleted (blowfish.h) — prevents accidental key material copies
  5. Constants moved inside include guards (blowfish.h, blowfish2.h)

  Code Quality Fixes

  6. Typo fixed — BF_SBOX_INT → BF_SBOX_INIT in blowfish.cc
  7. CMake standard fixed — blowfish2 target now requires cxx_std_17 instead of cxx_std_14

  Test Fixes & Additions

  8. Fixed "no fixed points" bug (test_properties.cpp) — L is no longer always 0
  9. Eric Young KAT vectors (test_vectors.cpp) — 5 official Blowfish test vectors added
  10. Key length tests — min (1 byte), max (56 bytes), and differing lengths
  11. Invalid key rejection tests — empty, over-length, and null keys
  12. Edge-case blocks — all-zero, all-ones, L==R
  13. Key avalanche tests — flipping each key bit produces large ciphertext changes
  14. Cross-instance consistency — same key → same output across instances
  15. Re-initialization tests — different key after re-init produces different output

Assisted-by: Claude Code

Signed-off-by: Avinal Kumar <avinal.xlvii@gmail.com>

CMakeLists.txt

@@ -29,7 +29,7 @@ target_include_directories(blowfish PUBLIC ${BF_INCLUDE_DIR})
 
 # ===== blowfish2 library =====
 add_library(blowfish2)
-target_compile_features(blowfish2 PUBLIC cxx_std_14)
+target_compile_features(blowfish2 PUBLIC cxx_std_17)
 
 target_sources(blowfish2
     PRIVATE