ATECC508A加密芯片

ATECC508A加密芯片使用

开一个帖子交流下ATECC508A，也包括同类型芯片ATSHA208A

• demo使用
• 串口调试
• ConfigZone配置
• DataZone配置
• 加密读写
• 挑战（challenge）应答及校验
• Openssl相关
• 证书相关

---

demo使用

目前官网上能下载到的demo有cryptoauth-node-auth-basic和cryptoauth-d21-host
接下来的问题围绕着demo中代码展开讨论

串口调试

使用的是官方的开发板进行了测试

ConfigZone配置

datasheet中的说明如下图

重点说一下ReadKey和WriteKey，恰恰是这两个简单的说明，让人不清楚这两个参数如何使用。
在bit6和bit7配置为1的时候，本slot需要加密读或者写，所以需要秘钥，这个秘钥是需要存储在parent slot中的，这个parent slot的ID就是这两个Key。所以加密读写slot的时候，需要首先在parent key的slot中写入秘钥，然后再修改需要加密读写的slot。

DataZone配置

待补充

Demo数据分析

Demo中提供了一套配置参数，解析如下

tatic const uint8_t g_ecc_configdata[128] = {
0x01, 0x23, 0x00, 0x00, 0x00, 0x00, 0x50, 0x00, 0x04, 0x05, 0x06, 0x07, 0xEE, 0x00, 0x01, 0x00,
0xC0, 0x00, 0x55, 0x00, 0x8F, 0x20, 0xC4, 0x44, 0x87, 0x20, 0xC4, 0x44, 0x8F, 0x0F, 0x8F, 0x8F,
0x9F, 0x8F, 0x83, 0x64, 0xC4, 0x44, 0xC4, 0x44, 0x0F, 0x0F, 0x0F, 0x0F, 0x0F, 0x0F, 0x0F, 0x0F,
0x0F, 0x0F, 0x0F, 0x0F, 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xFF, 0xFF, 0xFF,
0x00, 0x00, 0x00, 0x00, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x33, 0x00, 0x1C, 0x00, 0x13, 0x00, 0x1C, 0x00, 0x3C, 0x00, 0x1C, 0x00, 0x1C, 0x00, 0x33, 0x00,
0x1C, 0x00, 0x1C, 0x00, 0x3C, 0x00, 0x3C, 0x00, 0x3C, 0x00, 0x3C, 0x00, 0x3C, 0x00, 0x3C, 0x00 };

利用程序分析如下：

serial NUM: 0x01 0x23 0x00 0x00 0x04 0x05 0x06 0x07 0xee
I2C enable: 0x01
I2C address: 0xc0
check mac: 0x00
OPT mode: 0x55
chip mode: 0x00
slot00 config: 0x8f 0x20 ; ReadKey:0B1111; NoMac:0; LimitUse:0; EncryptRead:0; IsSecret:1; WriteKey:0B0000; WriteConfig:0B0010;
slot01 config: 0xc4 0x44 ; ReadKey:0B0100; NoMac:0; LimitUse:0; EncryptRead:1; IsSecret:1; WriteKey:0B0100; WriteConfig:0B0100;
slot02 config: 0x87 0x20 ; ReadKey:0B0111; NoMac:0; LimitUse:0; EncryptRead:0; IsSecret:1; WriteKey:0B0000; WriteConfig:0B0010;
slot03 config: 0xc4 0x44 ; ReadKey:0B0100; NoMac:0; LimitUse:0; EncryptRead:1; IsSecret:1; WriteKey:0B0100; WriteConfig:0B0100;
slot04 config: 0x8f 0x0f ; ReadKey:0B1111; NoMac:0; LimitUse:0; EncryptRead:0; IsSecret:1; WriteKey:0B1111; WriteConfig:0B0000;
slot05 config: 0x8f 0x8f ; ReadKey:0B1111; NoMac:0; LimitUse:0; EncryptRead:0; IsSecret:1; WriteKey:0B1111; WriteConfig:0B1000;
slot06 config: 0x9f 0x8f ; ReadKey:0B1111; NoMac:1; LimitUse:0; EncryptRead:0; IsSecret:1; WriteKey:0B1111; WriteConfig:0B1000;
slot07 config: 0x83 0x64 ; ReadKey:0B0011; NoMac:0; LimitUse:0; EncryptRead:0; IsSecret:1; WriteKey:0B0100; WriteConfig:0B0110;
slot08 config: 0xc4 0x44 ; ReadKey:0B0100; NoMac:0; LimitUse:0; EncryptRead:1; IsSecret:1; WriteKey:0B0100; WriteConfig:0B0100;
slot09 config: 0xc4 0x44 ; ReadKey:0B0100; NoMac:0; LimitUse:0; EncryptRead:1; IsSecret:1; WriteKey:0B0100; WriteConfig:0B0100;
slot10 config: 0x0f 0x0f ; ReadKey:0B1111; NoMac:0; LimitUse:0; EncryptRead:0; IsSecret:0; WriteKey:0B1111; WriteConfig:0B0000;
slot11 config: 0x0f 0x0f ; ReadKey:0B1111; NoMac:0; LimitUse:0; EncryptRead:0; IsSecret:0; WriteKey:0B1111; WriteConfig:0B0000;
slot12 config: 0x0f 0x0f ; ReadKey:0B1111; NoMac:0; LimitUse:0; EncryptRead:0; IsSecret:0; WriteKey:0B1111; WriteConfig:0B0000;
slot13 config: 0x0f 0x0f ; ReadKey:0B1111; NoMac:0; LimitUse:0; EncryptRead:0; IsSecret:0; WriteKey:0B1111; WriteConfig:0B0000;
slot14 config: 0x0f 0x0f ; ReadKey:0B1111; NoMac:0; LimitUse:0; EncryptRead:0; IsSecret:0; WriteKey:0B1111; WriteConfig:0B0000;
slot15 config: 0x0f 0x0f ; ReadKey:0B1111; NoMac:0; LimitUse:0; EncryptRead:0; IsSecret:0; WriteKey:0B1111; WriteConfig:0B0000;
counter 0: 0xff 0xff 0xff 0xff 0x00 0x00 0x00 0x00
counter 1: 0xff 0xff 0xff 0xff 0x00 0x00 0x00 0x00
LastKeyUse:0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff
UserEctrax: 0x00
SelectorX: 0x00
LockValue: 0x00
LockConfig: 0x00
SlotLockedX: 0xff 0xff
Rfu90: 0x00 0x00
X509Format : 0x00 0x00 0x00 0x00
KeyConfig00 config: 0x33 0x00 ; Private:1; Pubinfo:1; KeyType:0B100;
KeyConfig01 config: 0x1c 0x00 ; Private:0; Pubinfo:0; KeyType:0B111;
KeyConfig02 config: 0x13 0x00 ; Private:1; Pubinfo:1; KeyType:0B100;
KeyConfig03 config: 0x1c 0x00 ; Private:0; Pubinfo:0; KeyType:0B111;
KeyConfig04 config: 0x3c 0x00 ; Private:0; Pubinfo:0; KeyType:0B111;
KeyConfig05 config: 0x1c 0x00 ; Private:0; Pubinfo:0; KeyType:0B111;
KeyConfig06 config: 0x1c 0x00 ; Private:0; Pubinfo:0; KeyType:0B111;
KeyConfig07 config: 0x33 0x00 ; Private:1; Pubinfo:1; KeyType:0B100;
KeyConfig08 config: 0x1c 0x00 ; Private:0; Pubinfo:0; KeyType:0B111;
KeyConfig09 config: 0x1c 0x00 ; Private:0; Pubinfo:0; KeyType:0B111;
KeyConfig10 config: 0x3c 0x00 ; Private:0; Pubinfo:0; KeyType:0B111;
KeyConfig11 config: 0x3c 0x00 ; Private:0; Pubinfo:0; KeyType:0B111;
KeyConfig12 config: 0x3c 0x00 ; Private:0; Pubinfo:0; KeyType:0B111;
KeyConfig13 config: 0x3c 0x00 ; Private:0; Pubinfo:0; KeyType:0B111;
KeyConfig14 config: 0x3c 0x00 ; Private:0; Pubinfo:0; KeyType:0B111;
KeyConfig15 config: 0x3c 0x00 ; Private:0; Pubinfo:0; KeyType:0B111;

加密读写

Datasheet上表示了加密读写的两种用法，但是描述不清楚，或者因为个人理解有限吧。
参照**cryptoauth-node-auth-basic**demo中的函数说明，测试了加密读写接口，文件为atca_basic.c文件中的两个函数
加密写接口如下

/** \brief Write 32 bytes of data into given slot.
 *      The function takes clear text bytes, but encrypts them for writing over the wire
 *      Data zone must be locked and the slot configuration must be set to encrypted write for the block to be successfully written
 *  \param[in] slotid
 *  \param[in] block
 *  \param[in] data      The 32 bytes of clear text data to be written to the slot
 *  \param[in] enckey    The key to encrypt with for writing
 *  \param[in] enckeyid  The keyid of the parent encryption key
 *  returns ATCA_STATUS
 */
ATCA_STATUS atcab_write_enc(uint8_t slotid, uint8_t block, const uint8_t *data, const uint8_t* enckey, const uint16_t enckeyid)

加密读接口如下

/** \brief Read 32 bytes of data from the given slot.
 *      The function returns clear text bytes. Encrypted bytes are read over the wire, then subsequently decrypted
 *      Data zone must be locked and the slot configuration must be set to encrypted read for the block to be successfully read
 *  \param[in]  slotid    The slot id for the encrypted read
 *  \param[in]  block     The block id in the specified slot
 *  \param[out] data      The 32 bytes of clear text data that was read encrypted from the slot, then decrypted
 *  \param[in]  enckey    The key to encrypt with for writing
 *  \param[in]  enckeyid  The keyid of the parent encryption key
 *  returns ATCA_STATUS
 */
ATCA_STATUS atcab_read_enc(uint8_t slotid, uint8_t block, uint8_t *data, const uint8_t* enckey, const uint16_t enckeyid)

目前疑惑的地方就是这个enckey参数，究竟是从哪里来的，我随意写出来的enckey参数，加密写入没问题，但是读取的时候，就会返回出来错误的数据，与写入的不一致，希望能有人一起讨论一下
2017-10-11 15:51（修改）
问题已经解决，这个enckey是需要首先写入芯片，作为存储秘钥的slot的parent slot，并且这个enckye在随后向slot写入和读取秘钥的时候，都是作为必备参数的。

挑战（challenge）应答及校验

芯片本身的挑战响应与校验方式很简单，参照文件node_auth.c中的两个函数，改写测试函数如下
slot0提供公钥，host得到公钥保存起来。

static int get_pub_key(void)
{
    int ret = 0;
    int i = 0;


    //slot0上生成key
    ret = atcab_genkey(0, device_public_key);
    if (ret != ATCA_SUCCESS) return ret;

    printf("\r\n device_public_key:");
    for(i=0;i<64;i++)
    {
        printf("0x%02x,",device_public_key[i]);
    }
    printf("\r\n"); 

    char displaystr[256];
    int displaylen = sizeof(displaystr);    

    atcab_bin2hex(device_public_key, 64, displaystr, &displaylen );
    printf("\r\n device_public_key:\r\n%s\r\n", displaystr);

    return 0;

}

host随机一个挑战，发送给芯片，芯片用slot0做出应答，
挑战应答函数如下

static int get_response(void)
{
    int ret = 0;
    int i = 0;

    //设备使用slot0响应challenge，得到response
    ret = atcacert_get_response(0, s_challenge, s_response);
    if (ret != ATCACERT_E_SUCCESS) return ret;

    printf("\r\n s_response:");
    for(i=0;i<64;i++)
    {
        printf("0x%02x,",s_response[i]);
    }
    printf("\r\n");

    char displaystr[256];
    int displaylen = sizeof(displaystr);    

    atcab_bin2hex(s_response, 64, displaystr, &displaylen );
    printf("\r\n s_response:\r\n%s\r\n", displaystr);
    return 0;
}

这样host拥有了公钥，挑战，和挑战应答，就可以验证芯片是否合法有效了

芯片本身也可以检查其他人发送过来的，公钥，挑战和应答是否合法有效
应答检查函数如下

static int check_response(void)
{
    int ret = 0;
    int i = 0;
    char displaystr[256];
    int displaylen = sizeof(displaystr);    
    char displaystr2[256];
    int displaylen2 = sizeof(displaystr);   
    char displaystr3[256];
    int displaylen3 = sizeof(displaystr);   



    //检验设备应答
    ret = atcacert_verify_response_hw(device_public_key, s_challenge, s_response);


    printf("\r\n device_public_key:");
    for(i=0;i<64;i++)
    {
        printf("0x%02x,",device_public_key[i]);
    }
    printf("\r\n");  

    atcab_bin2hex(device_public_key, 64, displaystr, &displaylen );
    printf("\r\n device_public_key:\r\n%s\r\n", displaystr);

    printf("\r\n s_challenge:");
    for(i=0;i<32;i++)
    {
        printf("0x%02x,",s_challenge[i]);
    }
    printf("\r\n");  

    memset(displaystr,0x0,256);
    atcab_bin2hex(s_challenge, 32, displaystr2, &displaylen2 );
    printf("\r\n s_challenge:\r\n%s\r\n", displaystr2);


    printf("\r\n s_response:");
    for(i=0;i<64;i++)
    {
        printf("0x%02x,",s_response[i]);
    }
    printf("\r\n");  

    memset(displaystr,0x0,256);
    atcab_bin2hex(s_response, 64, displaystr3, &displaylen3 );
    printf("\r\n s_response:\r\n%s\r\n", displaystr3);


    if (ret != ATCACERT_E_SUCCESS)
    {
            printf("HOST: Device response to challenge fail!\r\n");
    }
    else
    {
            printf("HOST: Device response to challenge verified!\r\n");

    }

    return ret;
}

Openssl相关

之所以提到Openssl，例如在检查挑战应答是否合法的时候，是在host里面，如果host里面没有ATECC508芯片的话，那就需要软件实现ECDSA算法来校验应答是否正确

网上查看了相关同学的博客，也没有找到合适的C语言代码
结合openssl的头文件，找到了一个相关函数
说明如下

/** Verifies that the given signature is valid ECDSA signature
 *  of the supplied hash value using the specified public key.
 *  \param  type     this parameter is ignored
 *  \param  dgst     pointer to the hash value
 *  \param  dgstlen  length of the hash value
 *  \param  sig      pointer to the DER encoded signature
 *  \param  siglen   length of the DER encoded signature
 *  \param  eckey    EC_KEY object containing a public EC key
 *  \return 1 if the signature is valid, 0 if the signature is invalid
 *          and -1 on error
 */
int ECDSA_verify(int type, const unsigned char *dgst, int dgstlen,
                 const unsigned char *sig, int siglen, EC_KEY *eckey);

2017-10-12 补充
编写了一段代码模拟主机验证挑战、应答和公钥的正确性

#include 
#include 
#include 
#include 
#include 

#define MAXSIGLEN  128 

// 公钥
static const unsigned char pubkey[64] = 
    {0x6a,0x06,0x81,0x17,0x1a,0x20,0xa1,0x4b,0xed,0x75,
    0x14,0xc9,0x81,0xc0,0x03,0xfc,0x4a,0x28,0x11,0x58,
    0x08,0xc2,0x0b,0xf5,0x99,0xc2,0x3b,0x33,0x33,0x50,
    0xb6,0x17,0x69,0x0d,0x56,0x05,0x3a,0xe4,0x06,0x49,
    0xc3,0x3f,0xbb,0x0c,0xa3,0xaf,0x91,0xc5,0x26,0x20,
    0xc5,0xa7,0x55,0xdf,0x33,0xd7,0x9e,0x82,0xba,0x9a,
    0x57,0x3f,0x12,0x6c}; 

unsigned char challenge[32]=
    {0x0c,0xa6,0x34,0xc8,0x37,0x2f,0x87,0x99,0x99,0x7e,
    0x9e,0xe9,0xd5,0xbc,0x72,0x71,0x84,0xd1,0x97,0x0a,
    0xea,0xfe,0xac,0x60,0x7e,0xd1,0x3e,0x12,0xb7,0x32,0x25,0xf1};
unsigned char response[64]=
    {0x46,0x59,0x81,0xfd,0x7b,0xb3,0xc9,0x78,0x9f,0x12,
    0x33,0x8b,0x3a,0x6a,0x3c,0x07,0xaa,0x64,0x1d,0xa9,
    0xf5,0x5a,0x6f,0x26,0x40,0xc2,0x6f,0x2d,0x39,0xe1,
    0x80,0xc1,0xe4,0x2e,0xfb,0x9a,0xc2,0x05,0xd9,0xb3,
    0x82,0xe2,0x9b,0xe5,0xf2,0xd0,0x5b,0x0b,0xaf,0x6c,
    0xf1,0x27,0x88,0xc6,0x74,0xec,0xf7,0x88,0xc0,0xae,
    0xdc,0x0c,0x83,0x6a};

 /* 验证函数 */ 
static int verify(int keytype,const unsigned char *sig,int siglen,const unsigned char *dig,int dig_len)
{
    int ret;
    EC_KEY *ec_key = NULL;
    EC_GROUP *ec_group;
    unsigned char *pp = (unsigned char*)pubkey;


    if ((ec_key = EC_KEY_new()) == NULL)
    {
        printf("Error：EC_KEY_new();");
        return -1;
    }
    if ((ec_group = EC_GROUP_new_by_curve_name(keytype)) == NULL)
    {
        printf("Error：EC_GROUP_new_by_curve_name()\n");
        EC_KEY_free(ec_key);
        return -1;
    }

    /* 设置密钥参数 */
    ret=EC_KEY_set_group(ec_key,ec_group);
    if(ret!=1)
    {
        printf("Error:EC_KEY_set_group;");
        EC_KEY_free(ec_key);
        return -1;
    }

    /* 导入公钥 */
    ec_key = o2i_ECPublicKey(&ec_key,(const unsigned char**)&pp,sizeof(pubkey));
    if (ec_key == NULL)
    {
        printf("Error:o2i_ECPublicKey ;");
        EC_KEY_free(ec_key);
        return 0;
    }  

    /*
    ret=EC_KEY_oct2key(ec_key,pubkey,64,NULL);
    if(ret!=1)
    {
        printf("Error:EC_KEY_oct2priv;");
        EC_KEY_free(ec_key);
        return -1;
    }
    */
    /* 验证签名 */
    ret = ECDSA_verify(0,(const unsigned char*)dig, dig_len, sig, siglen,ec_key);  
    EC_KEY_free(ec_key);
    return ret == 1 ? 1 : 0;
}  

/* 主函数 */
int main(int argc, char* argv[]) 
{
       EC_builtin_curve    *curves;

       int                 i,crv_len;
    unsigned char digest[32]={};
    unsigned int  dgst_len = 0;

    EVP_MD_CTX *md_ctx = EVP_MD_CTX_new();
    EVP_DigestInit(md_ctx, EVP_sha256()); // 散列算法
    EVP_DigestUpdate(md_ctx, (const void*)challenge,32);
    EVP_DigestFinal(md_ctx, digest, &dgst_len);


    printf("digest:");
    for(i=0;iprintf("0x%02x ",digest[i]);
    }
    printf("\r\n");

    /* 获取实现的椭圆曲线个数 */
       crv_len = EC_get_builtin_curves(NULL, 0);
       curves = (EC_builtin_curve *)malloc(sizeof(EC_builtin_curve) * crv_len);
       /* 获取椭圆曲线列表 */
       EC_get_builtin_curves(curves, crv_len);

    for(i=0;i//printf("curves[%d]:[%d]%s \r\n",i,curves[i].nid,curves[i].comment);
        int ret = verify(curves[i].nid,(const unsigned char *)&response,sizeof(response),(const unsigned char *)&digest,dgst_len);
        if(ret==1)
        {
            printf("|keytype:[%d]:[%s] Verify:OK\n",curves[i].nid,curves[i].comment);
        }
        else
        {
            printf("|keytype:[%d]:[%s] Verify:Error\n",curves[i].nid,curves[i].comment);
        }
    }
    return 0;
}

目前还是存在问题，o2i_ECPublicKey将秘钥从buffer导出成EC_KEY格式的时候一直有问题，目前尚不清楚原因为何

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