BLAKE2s ハッシュ関数実装の追加

新規ファイル:
- include/se050_blake2s.h: BLAKE2s API ヘッダー
- src/se050_blake2s.c: BLAKE2s 実装

機能:
- BLAKE2s-256 ハッシュ（RFC 7693）
- 可変長キー対応（最大 64 バイト）
- 可変長出力（1-32 バイト）
- ESP32 32 ビット最適化
- 安全な関数使用（memzero_explicit）

WireGuard 固有関数:
- se050_wireguard_derive_key(): キー導出
- se050_wireguard_generate_secret(): シークレット生成

API:
- se050_blake2s_init()
- se050_blake2s_init_key()
- se050_blake2s_update()
- se050_blake2s_final()
- se050_blake2s() (one-shot)
- se050_blake2s_keyed() (one-shot with key)

テスト:
- BLAKE2S_TEST マクロでテストビルド
- RFC 7693 テストベクトル（実装修正必要）

注：RFC 7693 テストベクトル通過には圧縮関数のさらなる修正が必要

include/se050_blake2s.h

@@ -0,0 +1,157 @@
+/**
+ * @file se050_blake2s.h
+ * @brief BLAKE2s Hash Function Implementation
+ * 
+ * Based on RFC 7693. Supports variable-length keys and outputs.
+ * Used in WireGuard for key derivation.
+ * 
+ * License: MIT (Clean-room implementation)
+ */
+
+#ifndef SE050_BLAKE2S_H
+#define SE050_BLAKE2S_H
+
+#include <stdint.h>
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* ============================================================================
+ * Constants
+ * ============================================================================ */
+
+#define BLAKE2S_BLOCK_SIZE    64
+#define BLAKE2S_DIGEST_SIZE   32
+#define BLAKE2S_KEY_SIZE      64
+#define BLAKE2S_MIN_KEY_SIZE  1
+#define BLAKE2S_MAX_KEY_SIZE  64
+#define BLAKE2S_MIN_OUTLEN    1
+#define BLAKE2S_MAX_OUTLEN    32
+
+/* ============================================================================
+ * Type Definitions
+ * ============================================================================ */
+
+/**
+ * @brief BLAKE2s context
+ */
+typedef struct {
+    uint32_t h[8];          /* Hash state */
+    uint32_t t[2];          /* Counter */
+    uint32_t f[2];          /* Block flag */
+    uint8_t  buf[BLAKE2S_BLOCK_SIZE];  /* Input buffer */
+    size_t   buflen;        /* Current buffer size */
+    size_t   outlen;        /* Desired output length */
+    uint8_t  last_node;     /* Last node flag */
+} se050_blake2s_ctx_t;
+
+/* ============================================================================
+ * API Functions
+ * ============================================================================ */
+
+/**
+ * @brief Initialize BLAKE2s context
+ * 
+ * @param ctx Context to initialize
+ * @param outlen Output length (1-32 bytes)
+ * @return 0 on success, -1 on error
+ */
+int se050_blake2s_init(se050_blake2s_ctx_t *ctx, size_t outlen);
+
+/**
+ * @brief Initialize BLAKE2s with key
+ * 
+ * @param ctx Context to initialize
+ * @param outlen Output length (1-32 bytes)
+ * @param key Key (1-64 bytes)
+ * @param keylen Key length
+ * @return 0 on success, -1 on error
+ */
+int se050_blake2s_init_key(se050_blake2s_ctx_t *ctx, size_t outlen,
+                           const void *key, size_t keylen);
+
+/**
+ * @brief Update hash with data
+ * 
+ * @param ctx Context
+ * @param data Data to hash
+ * @param len Data length
+ * @return 0 on success, -1 on error
+ */
+int se050_blake2s_update(se050_blake2s_ctx_t *ctx, const void *data, size_t len);
+
+/**
+ * @brief Finalize hash and get digest
+ * 
+ * @param ctx Context
+ * @param out Output buffer (at least outlen bytes)
+ * @param outlen Output length
+ * @return 0 on success, -1 on error
+ */
+int se050_blake2s_final(se050_blake2s_ctx_t *ctx, void *out, size_t outlen);
+
+/**
+ * @brief Compute BLAKE2s hash (one-shot)
+ * 
+ * @param out Output buffer (at least outlen bytes)
+ * @param outlen Output length
+ * @param data Data to hash
+ * @param len Data length
+ * @return 0 on success, -1 on error
+ */
+int se050_blake2s(void *out, size_t outlen, const void *data, size_t len);
+
+/**
+ * @brief Compute BLAKE2s hash with key (one-shot)
+ * 
+ * @param out Output buffer (at least outlen bytes)
+ * @param outlen Output length
+ * @param key Key
+ * @param keylen Key length
+ * @param data Data to hash
+ * @param len Data length
+ * @return 0 on success, -1 on error
+ */
+int se050_blake2s_keyed(void *out, size_t outlen, const void *key, size_t keylen,
+                        const void *data, size_t len);
+
+/**
+ * @brief Securely zeroize context
+ * 
+ * @param ctx Context to zeroize
+ */
+void se050_blake2s_zeroize(se050_blake2s_ctx_t *ctx);
+
+/* ============================================================================
+ * WireGuard-Specific Functions
+ * ============================================================================ */
+
+/**
+ * @brief WireGuard key derivation using BLAKE2s
+ * 
+ * Computes: BLAKE2s("wireguard key derivation", input, 32)
+ * 
+ * @param out Output (32 bytes)
+ * @param input Input data
+ * @param inlen Input length
+ * @return 0 on success, -1 on error
+ */
+int se050_wireguard_derive_key(uint8_t out[32], const uint8_t *input, size_t inlen);
+
+/**
+ * @brief WireGuard secret key generation
+ * 
+ * @param out Output (32 bytes)
+ * @param input Input data
+ * @param inlen Input length
+ * @return 0 on success, -1 on error
+ */
+int se050_wireguard_generate_secret(uint8_t out[32], const uint8_t *input, size_t inlen);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SE050_BLAKE2S_H */