1 files changed, 211 insertions, 0 deletions
diff --git a/archive/2025/summer/bsc_karidas/src/Crypto.cpp b/archive/2025/summer/bsc_karidas/src/Crypto.cpp
new file mode 100644
index 000000000..0e7912721
--- /dev/null
+++ b/archive/2025/summer/bsc_karidas/src/Crypto.cpp
@@ -0,0 +1,211 @@
+#include "Crypto.hpp"
+#include <openssl/evp.h>
+#include <openssl/rand.h>
+#include <openssl/err.h>
+#include <stdexcept>
+#include <cstring>
+#include <iostream>
+
+Crypto::Crypto()
+{
+    // Initialize OpenSSL
+    OpenSSL_add_all_algorithms();
+    m_encryptCtx = EVP_CIPHER_CTX_new();
+    if (!m_encryptCtx)
+    {
+        throw std::runtime_error("Failed to create encryption context");
+    }
+
+    m_decryptCtx = EVP_CIPHER_CTX_new();
+    if (!m_decryptCtx)
+    {
+        EVP_CIPHER_CTX_free(m_encryptCtx);
+        throw std::runtime_error("Failed to create decryption context");
+    }
+}
+
+Crypto::~Crypto()
+{
+    // Free contexts
+    if (m_encryptCtx)
+    {
+        EVP_CIPHER_CTX_free(m_encryptCtx);
+    }
+
+    if (m_decryptCtx)
+    {
+        EVP_CIPHER_CTX_free(m_decryptCtx);
+    }
+
+    // Clean up OpenSSL
+    EVP_cleanup();
+}
+
+// Encrypt data using AES-256-GCM with provided IV
+std::vector<uint8_t> Crypto::encrypt(std::vector<uint8_t> &&plaintext,
+                                     const std::vector<uint8_t> &key,
+                                     const std::vector<uint8_t> &iv)
+{
+    if (plaintext.empty())
+        return {};
+    if (key.size() != KEY_SIZE)
+        throw std::runtime_error("Invalid key size");
+    if (iv.size() != GCM_IV_SIZE)
+        throw std::runtime_error("Invalid IV size");
+
+    // Reset the existing context instead of creating a new one
+    EVP_CIPHER_CTX_reset(m_encryptCtx);
+
+    // Initialize encryption operation
+    if (EVP_EncryptInit_ex(m_encryptCtx, EVP_aes_256_gcm(), nullptr, key.data(), iv.data()) != 1)
+    {
+        throw std::runtime_error("Failed to initialize encryption");
+    }
+
+    // Calculate the exact output size: size_field + ciphertext + tag
+    // For GCM mode, ciphertext size equals plaintext size (no padding)
+    const size_t sizeFieldSize = sizeof(uint32_t);
+    const size_t ciphertextSize = plaintext.size();
+    const size_t totalSize = sizeFieldSize + ciphertextSize + GCM_TAG_SIZE;
+
+    // Pre-allocate result buffer with exact final size
+    std::vector<uint8_t> result(totalSize);
+
+    // Reserve space for data size field
+    uint32_t dataSize = ciphertextSize;
+    std::memcpy(result.data(), &dataSize, sizeFieldSize);
+
+    // Perform encryption directly into the result buffer (after the size field)
+    int encryptedLen = 0;
+    if (EVP_EncryptUpdate(m_encryptCtx, result.data() + sizeFieldSize, &encryptedLen,
+                          plaintext.data(), plaintext.size()) != 1)
+    {
+        throw std::runtime_error("Failed during encryption update");
+    }
+
+    // Finalize encryption (writing to the buffer right after the existing encrypted data)
+    int finalLen = 0;
+    if (EVP_EncryptFinal_ex(m_encryptCtx, result.data() + sizeFieldSize + encryptedLen, &finalLen) != 1)
+    {
+        throw std::runtime_error("Failed to finalize encryption");
+    }
+
+    // Sanity check: for GCM, encryptedLen + finalLen should equal plaintext.size()
+    if (encryptedLen + finalLen != static_cast<int>(plaintext.size()))
+    {
+        throw std::runtime_error("Unexpected encryption output size");
+    }
+
+    // Get the authentication tag and write it directly to the result buffer
+    if (EVP_CIPHER_CTX_ctrl(m_encryptCtx, EVP_CTRL_GCM_GET_TAG, GCM_TAG_SIZE,
+                            result.data() + sizeFieldSize + ciphertextSize) != 1)
+    {
+        throw std::runtime_error("Failed to get authentication tag");
+    }
+
+    return result;
+}
+
+// Decrypt data using AES-256-GCM with provided IV
+std::vector<uint8_t> Crypto::decrypt(const std::vector<uint8_t> &encryptedData,
+                                     const std::vector<uint8_t> &key,
+                                     const std::vector<uint8_t> &iv)
+{
+    try
+    {
+        if (encryptedData.empty())
+        {
+            return std::vector<uint8_t>();
+        }
+
+        // Validate key size
+        if (key.size() != KEY_SIZE)
+        {
+            throw std::runtime_error("Invalid key size. Expected 32 bytes for AES-256");
+        }
+
+        // Validate IV size
+        if (iv.size() != GCM_IV_SIZE)
+        {
+            throw std::runtime_error("Invalid IV size. Expected 12 bytes for GCM");
+        }
+
+        // Ensure we have at least enough data for the data size field
+        if (encryptedData.size() < sizeof(uint32_t))
+        {
+            throw std::runtime_error("Encrypted data too small - missing data size");
+        }
+
+        // Extract the encrypted data size
+        uint32_t dataSize;
+        std::memcpy(&dataSize, encryptedData.data(), sizeof(dataSize));
+        size_t position = sizeof(dataSize);
+
+        // Validate data size
+        if (position + dataSize > encryptedData.size())
+        {
+            throw std::runtime_error("Encrypted data too small - missing complete data");
+        }
+
+        // Extract the encrypted data
+        std::vector<uint8_t> ciphertext(dataSize);
+        std::memcpy(ciphertext.data(), encryptedData.data() + position, dataSize);
+        position += dataSize;
+
+        // Extract the authentication tag
+        if (position + GCM_TAG_SIZE > encryptedData.size())
+        {
+            throw std::runtime_error("Encrypted data too small - missing authentication tag");
+        }
+
+        std::vector<uint8_t> tag(GCM_TAG_SIZE);
+        std::memcpy(tag.data(), encryptedData.data() + position, GCM_TAG_SIZE);
+
+        // Reset the existing context instead of creating a new one
+        EVP_CIPHER_CTX_reset(m_decryptCtx);
+
+        // Initialize decryption operation
+        if (EVP_DecryptInit_ex(m_decryptCtx, EVP_aes_256_gcm(), nullptr, key.data(), iv.data()) != 1)
+        {
+            throw std::runtime_error("Failed to initialize decryption");
+        }
+
+        // Set expected tag value
+        if (EVP_CIPHER_CTX_ctrl(m_decryptCtx, EVP_CTRL_GCM_SET_TAG, GCM_TAG_SIZE, tag.data()) != 1)
+        {
+            throw std::runtime_error("Failed to set authentication tag");
+        }
+
+        // Prepare output buffer for plaintext
+        std::vector<uint8_t> decryptedData(ciphertext.size());
+        int decryptedLen = 0;
+
+        // Perform decryption
+        if (EVP_DecryptUpdate(m_decryptCtx, decryptedData.data(), &decryptedLen,
+                              ciphertext.data(), ciphertext.size()) != 1)
+        {
+            throw std::runtime_error("Failed during decryption update");
+        }
+
+        // Finalize decryption and verify tag
+        int finalLen = 0;
+        int ret = EVP_DecryptFinal_ex(m_decryptCtx, decryptedData.data() + decryptedLen, &finalLen);
+
+        if (ret != 1)
+        {
+            throw std::runtime_error("Authentication failed: data may have been tampered with");
+        }
+
+        // Resize the decrypted data to the actual length
+        decryptedData.resize(decryptedLen + finalLen);
+
+        return decryptedData;
+    }
+    catch (const std::exception &e)
+    {
+        std::cerr << "Error decrypting data: " << e.what() << std::endl;
+        // Print OpenSSL error queue
+        ERR_print_errors_fp(stderr);
+        return std::vector<uint8_t>();
+    }
+}
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