数字证书格式编码

ASN.1描述与实例

1．TBSCertificate 的 ASN.1描述与实例

TBSCertificate格式用ASN.1描述如下:
TBSCertificate :=SEQUENCE {
version
[0] EXPLICIT Version DEFAULT v1,
serialNumber
CertificateSerialNumber,
signature
Algorithmldentifier,
issuer
Name,
validity
Validity,
subject
Name,
subjectPublicKeyInfo SubjectPublicKeyInfo,
issuerUniqueID[1] IMPLICIT Uniqueldentifier OPTIONAL,
-- If present, version MUST be v2 or v3

subjectUniqueID [2] IMPLICIT Uniqueldentifier OPTIONAL,
-- If present, version MUST be v2 or v3
extensions[3]EXPLICIT Extensions OPTIONAL
-- If present, version MUST be v3
}
Extensions ::=SEQUENCE SIZE (1..MAX) OF ExtensionTBSCertificate 中各项内容具体值如表13-3所示。

TBSCertificate	值
version	02
serialNumber	04 96
signature	sha 1 WithRSAEncryption ( 1.2.840.113549.1.1.5)
issuer	“CN=Virtual CA,C=CN”
validity	notBefore=20200222000000、notAfter=20220222000000
subject	“CN=chenshaoqing，OU=Person，C=CN”
subjectPublicKeyInfo
issuerUniquelD subjectUniquelD	空
extensions	包含6个扩展项（Extension ): basicContraints、subjectKeyldentifier、keyUsage、extKeyUsage,netscapeCertType、authorityKeyIdentifier

2. Extension的ASN.1描述与实例Extension格式用ASN.1描述如下:
Extension :=SEQUENCE {
extnID
OBJECT IDENTIFIER,
critical
BOOLEAN DEFAULT FALSE,
extnValue
OCTET STRING }
Extension各扩展项值如表13-4所示。

 

 

3. Certificate 的ASN.1描述与实例Certificate格式用ASN.1描述如下:
Certificate ::=SEQUENCE {
tbsCertificate
TBSCertificate,
signatureAlgorithm
AlgorithmIdentifier,
signature Value
BIT STRING }
Certificate中各项内容的具体值如表13-5所示。

DER编码过程
1．对Extension进行DER编码
各扩展项具体内容用ASN.1描述如下:
BasicConstraints ::=SEQUENCE{
cA
BOOLEAN DEFAULT FALSE,
pathLenConstraint
INTEGER (O..MAX)OPTIONAL}
SubjectKeyIdentifier ::= Keyldentifier
(KeyIdentifier ::= OCTET STRING)KeyUsage ::= BIT STRING
ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX)OF KeyPurposeld

(KeyPurposeld ::= OBJECT IDENTIFIER)NetscapeCertType ::= BIT STRING
AuthorityKeyldentifier ::=SEQUENCE{
keyIdentifier
[O] KeyIdentifier
OPTIONAL,
authorityCertIssuer
[1]GeneralNames
OPTIONAL,
authorityCertSerialNumber [2] CertificateSerialNumber OPTIONAL }(KeyIdentifier ::= OCTET STRING)
Extension为 SEQUENCE结构类型，不同扩展项DER编码值包含在OCTET STRING类型extnValue中，编码规则采用结构类型定长模式。各扩展项DER编码值用括号分隔。其中，对于BIT STRING类型，编码后第1个字节表示填充位数或未使用位数。

 

 

2．对TBSCertificate进行DER编码
TBSCertificate内容编码规则采用结构类型定长模式，具体编码过程如表13-7所示。

1、序列号=1174（0x0496）

echo -n -e "\xA0\x03\x02\x01\x02\x02\x02\x04\x96\x30\x0D\x06\x09\x2A\x86\x48\x86\xF7\x0D\x01\x01\x05\x05\x00" > 20181217.der

 

 

2、证书签发者 DN="CN=Virtual CA

echo -n -e "\x30\x22\x31\x0B\x30\x09\x06\x03\x55\x04\x06\x13\x02\x43\x4E\x31\x13\x30\x11\x06\x03\x55\x04\x03\x13\x0A\x56\x69\x72\x74\x75\x61\x6C\x20\x43\x41" >> 20181217.der

 

 

3、证书有效期=20200222000000-20220222000000

echo -n -e "\x17\x0D\x32\x30\x32\x30\x30\x32\x32\x32\x30\x30\x30\x30\x5A\x17\x0D\x32\x30\x32\x32\x30\x32\x32\x32\x30\x30\x30\x30\x5A" >> 20181217.der

 

 

4、证书持有者DN=CN=你的名字拼音， OU=Person

echo -n -e "\x30\x37\x31\x0b\x30\x09\x06\x03\x55\x04\x06\x13\x02\x43\x4e\x31\x11\x30\x0f\x06\x03\x55\x04\x0a\x13\x08\x32\x30\x31\x38\x31\x32\x31\x37\x31\x15\x30\x13\x06\x03\x55\x04\x03\x13\x0c\x63\x68\x65\x6E\x73\x68\x61\x6F\x71\x69\x6e\x67\x20" >> 20181217.der