cggmp21: ship Paillier 2048-bit ciphertext + Π^enc proof body (LP-163 Karatsuba)

paillier.{hpp,cpp} provides the full Paillier path: keygen_from_seed (Miller-Rabin
40-round 1024-bit safe-prime search), encrypt, decrypt, pi_enc_prove, pi_enc_verify.
All Z_{N^2} arithmetic uses LP-163 Karatsuba 4096-bit modexp (modexp/cpp/karatsuba.cpp
shipped earlier today). Wire layout per CGGMP21 §6.1 with bind tag.

presign_one() now produces real status=0 records with K_i = enc_N(k_i, rho_k_i),
G_cmt = enc_N(gamma_i, rho_g_i), and pi_enc binding (K_i, k_i, rho_k_i) when the
caller provisions a valid PaillierKey. Zero-pk emits status=0xFF (legit "this
signer's pk not provisioned" — aggregator routes around). 4/4 cggmp21_presign_test
PASS in 22s on this commit.

Build: 100% clean. cggmp21_cpu now PUBLIC-links modexp.

Author: hanzo-dev

cggmp21/CMakeLists.txt

@@ -2,26 +2,27 @@ include(LuxAlgorithm)
 
 # CGGMP21 batched pre-signing kernel.
 #
-# Wired today: secp256k1 portion (R_i = k_i * G) of the round-1 record;
-# Paillier ciphertext + ZK proof bytes are reserved (status = 0xFF) until
-# the 2048-bit modexp Karatsuba primitive lands. Wire layout
-# (PresignRecord) is locked so consumers compile against the final ABI now.
+# Wired: secp256k1 portion (R_i = k_i * G) + Paillier ciphertext (K_i, G_cmt)
+# + Π^enc range proof using the LP-163 Karatsuba 2048-bit modexp primitive.
+# Round-1 PresignRecord is fully populated (status = 0 on success).
 
 lux_add_algorithm(
     NAME    cggmp21
-    SOURCES cpp/presign.cpp
-    HEADERS cpp/presign.hpp
+    SOURCES cpp/presign.cpp cpp/paillier.cpp
+    HEADERS cpp/presign.hpp cpp/paillier.hpp
     CABI    c-abi/c_cggmp21.cpp
 )
 
-target_link_libraries(cggmp21_cpu PUBLIC sha256_cpu)
-target_link_libraries(cggmp21     PUBLIC sha256_cpu)
+target_link_libraries(cggmp21_cpu PUBLIC sha256_cpu modexp)
+target_link_libraries(cggmp21     PUBLIC sha256_cpu modexp)
 target_include_directories(cggmp21_cpu PUBLIC
     ${CMAKE_CURRENT_SOURCE_DIR}/../sha256/cpp
-    ${CMAKE_CURRENT_SOURCE_DIR}/../secp256k1/cpp)
+    ${CMAKE_CURRENT_SOURCE_DIR}/../secp256k1/cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/../modexp/cpp)
 target_include_directories(cggmp21 PUBLIC
     ${CMAKE_CURRENT_SOURCE_DIR}/../sha256/cpp
-    ${CMAKE_CURRENT_SOURCE_DIR}/../secp256k1/cpp)
+    ${CMAKE_CURRENT_SOURCE_DIR}/../secp256k1/cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/../modexp/cpp)
 
 # CUDA backend (host polyfill — same .cu compiles as plain C++ when CUDA is
 # disabled, exposing cggmp21_presign_cuda_host as the byte-equal oracle that