公钥证书编码解读

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一、文件编码

PEM (Privacy Enhancement Message)，定义见 RFC1421 是一种基于 base64 的编码格式，常见于 linux/unix 下的证书编码

结构组成 == {header} body {tail} 示例

DER (Distinguished Encoding Rules) , 定义见维基百科-ASN.1.DER
是来自ASN.1 体系的一种二进制编码格式，常用于 windows/mac 的证书编码

编码方式 == DER uses a pattern of type-length-value triplets

二、公钥标准

PKCS (Public Key Cryptography Standards)，定义见维基百科-PKCS
是一套公钥密码学标准，其定义范围涵盖了证书签名、加密算法、填充模式及校验流程等。

常见PKCS标准

三、RSA 密钥

RSA 公钥编码

PublicKey-PKCS#1-PEM

-----BEGIN RSA PUBLIC KEY-----
BASE64 ENCODED DATA
-----END RSA PUBLIC KEY-----

PublicKey-PKCS#1-DER

RSAPublicKey ::= SEQUENCE {
    modulus           INTEGER,  -- n
    publicExponent    INTEGER   -- e
}

PublicKey-PKCS#8-PEM

-----BEGIN PUBLIC KEY-----
BASE64 ENCODED DATA
-----END PUBLIC KEY-----

PublicKey-PKCS#8-DER

PublicKeyInfo ::= SEQUENCE {
  algorithm       AlgorithmIdentifier,
  PublicKey       BIT STRING
}

AlgorithmIdentifier ::= SEQUENCE {
  algorithm       OBJECT IDENTIFIER,
  parameters      ANY DEFINED BY algorithm OPTIONAL
}

对于RSA公钥来说，OID就是(1.2.840.113549.1.1.1)

RSA 私钥编码

PrivateKey-PKCS#1-PEM

-----BEGIN RSA PRIVATE KEY-----
BASE64 ENCODED DATA
-----END RSA PRIVATE KEY-----

PrivateKey-PKCS#1-DER

RSAPrivateKey ::= SEQUENCE {
  version           Version,
  modulus           INTEGER,  -- n
  publicExponent    INTEGER,  -- e
  privateExponent   INTEGER,  -- d
  prime1            INTEGER,  -- p
  prime2            INTEGER,  -- q
  exponent1         INTEGER,  -- d mod (p-1)
  exponent2         INTEGER,  -- d mod (q-1)
  coefficient       INTEGER,  -- (inverse of q) mod p
  otherPrimeInfos   OtherPrimeInfos OPTIONAL
}

PrivateKey-PKCS#8-PEM

-----BEGIN PRIVATE KEY-----
BASE64 ENCODED DATA
-----END PRIVATE KEY-----

PrivateKey-PKCS#8-DER

PrivateKeyInfo ::= SEQUENCE {
  version         Version,
  algorithm       AlgorithmIdentifier,
  PrivateKey      OCTET STRING
}

AlgorithmIdentifier ::= SEQUENCE {
  algorithm       OBJECT IDENTIFIER,
  parameters      ANY DEFINED BY algorithm OPTIONAL
}

私钥文件可采用加密方式存储，加密后的格式：
EncryptedPrivateKey-PKCS#8-PEM

-----BEGIN ENCRYPTED PRIVATE KEY-----
BASE64 ENCODED DATA
-----END ENCRYPTED PRIVATE KEY-----

Encrypted-PrivateKey-PKCS#8-DER

EncryptedPrivateKeyInfo ::= SEQUENCE {
  encryptionAlgorithm  EncryptionAlgorithmIdentifier,
  encryptedData        EncryptedData
}

EncryptionAlgorithmIdentifier ::= AlgorithmIdentifier

EncryptedData ::= OCTET STRING

四、证书

X.509 证书，维基百科-X.509，是目前流行的公钥证书标准。
一个 X.509 证书包含了一个公钥和对应的实体名(hostname/organization/individual)；证书通常由证书认证机构签名或自签名；当证书持有者被另外一方信任时(通过公钥签名验证)，两者便可以基于公钥算法建立安全传输通道。

证书结构

Certificate
Version Number
Serial Number
Signature Algorithm ID
Issuer Name
Validity period
Not Before
Not After
Subject name
Subject Public Key Info
Public Key Algorithm
Subject Public Key
Issuer Unique Identifier (optional)
Subject Unique Identifier (optional)
Extensions (optional)
...
Certificate Signature Algorithm
Certificate Signature

主要字段

扩展字段

样例-维基百科证书

Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number:
            10:e6:fc:62:b7:41:8a:d5:00:5e:45:b6
    Signature Algorithm: sha256WithRSAEncryption
        Issuer: C=BE, O=GlobalSign nv-sa, CN=GlobalSign Organization Validation CA - SHA256 - G2
        Validity
            Not Before: Nov 21 08:00:00 2016 GMT
            Not After : Nov 22 07:59:59 2017 GMT
        Subject: C=US, ST=California, L=San Francisco, O=Wikimedia Foundation, Inc., CN=*.wikipedia.org
        Subject Public Key Info:
            Public Key Algorithm: id-ecPublicKey
                Public-Key: (256 bit)
                pub: 
                    04:c9:22:69:31:8a:d6:6c:ea:da:c3:7f:2c:ac:a5:
                    af:c0:02:ea:81:cb:65:b9:fd:0c:6d:46:5b:c9:1e:
                    ed:b2:ac:2a:1b:4a:ec:80:7b:e7:1a:51:e0:df:f7:
                    c7:4a:20:7b:91:4b:20:07:21:ce:cf:68:65:8c:c6:
                    9d:3b:ef:d5:c1
                ASN1 OID: prime256v1
        X509v3 extensions:
            X509v3 Key Usage: critical
                Digital Signature, Key Agreement
            Authority Information Access: 
                CA Issuers - URI:http://secure.globalsign.com/cacert/gsorganizationvalsha2g2r1.crt
                OCSP - URI:http://ocsp2.globalsign.com/gsorganizationvalsha2g2

            X509v3 Certificate Policies: 
                Policy: 1.3.6.1.4.1.4146.1.20
                  CPS: https://www.globalsign.com/repository/
                Policy: 2.23.140.1.2.2

            X509v3 Basic Constraints: 
                CA:FALSE
            X509v3 CRL Distribution Points: 

                Full Name:
                  URI:http://crl.globalsign.com/gs/gsorganizationvalsha2g2.crl

            X509v3 Subject Alternative Name: 
                DNS:*.wikipedia.org, DNS:*.m.mediawiki.org, DNS:*.m.wikibooks.org, DNS:*.m.wikidata.org, DNS:*.m.wikimedia.org, DNS:*.m.wikimediafoundation.org, DNS:*.m.wikinews.org, DNS:*.m.wikipedia.org, DNS:*.m.wikiquote.org, DNS:*.m.wikisource.org, DNS:*.m.wikiversity.org, DNS:*.m.wikivoyage.org, DNS:*.m.wiktionary.org, DNS:*.mediawiki.org, DNS:*.planet.wikimedia.org, DNS:*.wikibooks.org, DNS:*.wikidata.org, DNS:*.wikimedia.org, DNS:*.wikimediafoundation.org, DNS:*.wikinews.org, DNS:*.wikiquote.org, DNS:*.wikisource.org, DNS:*.wikiversity.org, DNS:*.wikivoyage.org, DNS:*.wiktionary.org, DNS:*.wmfusercontent.org, DNS:*.zero.wikipedia.org, DNS:mediawiki.org, DNS:w.wiki, DNS:wikibooks.org, DNS:wikidata.org, DNS:wikimedia.org, DNS:wikimediafoundation.org, DNS:wikinews.org, DNS:wikiquote.org, DNS:wikisource.org, DNS:wikiversity.org, DNS:wikivoyage.org, DNS:wiktionary.org, DNS:wmfusercontent.org, DNS:wikipedia.org
            X509v3 Extended Key Usage: 
                TLS Web Server Authentication, TLS Web Client Authentication
            X509v3 Subject Key Identifier: 
                28:2A:26:2A:57:8B:3B:CE:B4:D6:AB:54:EF:D7:38:21:2C:49:5C:36
            X509v3 Authority Key Identifier: 
                keyid:96:DE:61:F1:BD:1C:16:29:53:1C:C0:CC:7D:3B:83:00:40:E6:1A:7C

    Signature Algorithm: sha256WithRSAEncryption
         8b:c3:ed:d1:9d:39:6f:af:40:72:bd:1e:18:5e:30:54:23:35:
         66:5e:62:d5:01:e2:63:47:70:cb:6d:1b:17:b0:f5:4d:11:e4:
         ad:94:51:c5:5e:72:03:b0:d5:ab:18:eb:b5:3a:08:a8:73:95:
         f3:7f:41:1a:28:7b:45:7c:83:2e:d3:14:95:d8:d5:d1:5f:99:
         4b:0c:f4:c3:9b:0b:4f:e9:49:f4:2c:b5:ae:c3:1d:7d:2a:80:
         f6:70:29:4c:0c:e6:e0:cb:88:8a:8a:02:ee:a5:d1:73:c2:93:
         58:24:ff:43:1b:e3:fd:7b:aa:f0:15:0c:60:52:8f:21:7d:87:
         3a:14:fa:81:41:00:60:4f:96:9a:62:94:58:de:cb:15:5c:3c:
         f4:c1:4d:33:e3:ff:39:fe:28:fb:b0:41:3e:d2:8a:11:d1:06:
         01:28:74:7d:71:d4:2a:ef:1f:e3:25:4b:2d:f0:66:ef:26:fb:
         4c:f0:81:85:bb:1a:99:06:c9:37:87:de:8d:49:f7:00:91:a9:
         42:31:4a:b9:40:a0:7d:4f:4f:a6:ea:d4:58:07:3c:01:e0:1a:
         53:54:66:e1:a3:7e:30:cd:3b:f8:69:59:a3:48:92:48:e1:9e:
         63:ab:08:70:91:f2:48:d2:83:4b:98:06:fa:fd:bc:99:02:da:
         9c:98:b1:a3

证书格式

PKI ITU-T X509标准，传统标准（.der .pem .cer .crt），仅包含公钥
PKCS#7 加密消息语法标准(.p7b .p7c .spc .p7r)，p7b/p7c/spc 包含了证书链，p7r是证书请求回复(非证书)
PKCS#10 证书请求标准(.p10)，.p10是证书请求文件，与.csr文件类似
PKCS#12 个人信息交换标准（.pfx *.p12），包含公钥和私钥，需密码保护

编码形式

X.509 DER(Distinguished Encoding Rules)编码，后缀为：.der .cer .crt
X.509 BASE64编码(PEM格式)，后缀为：.pem .cer .crt

X.509CRT-PEM

-----BEGIN CERTIFICATE-----
BASE64 ENCODED DATA
-----END CERTIFICATE-----

关键特性

编码形式：二进制还是ASCII
是否包含公钥、私钥
包含一个还是多个证书
是否支持密码保护（针对当前证书）

参考文档

mbed文档-公钥的der和pem编码格式比较
 Chen-PKI系统与数字证书结构

作者：美码师

欢迎添加华为云小助手微信（微信号：HWCloud002 或 HWCloud003），输入关键字“加群”，加入华为云线上技术讨论群；输入关键字“最新活动”，获取华为云最新特惠促销。华为云诸多技术大咖、特惠活动等你来撩

本文链接：https://www.cnblogs.com/huaweicloud/p/11861598.html