用户首先产生自己的密钥对，并将公共密钥及部分个人信息传送给CA(通过P10请求)
CertAndKeyGen gen = new CertAndKeyGen("RSA", "SHA1WithRSA");
gen.generate(1024);//生成1024位密钥
PKCS10CertificationRequestBuilder p10Builder = new JcaPKCS10CertificationRequestBuilder(
new X500Principal("CN = " + name), gen.getPublicKey());// CN和公钥
JcaContentSignerBuilder csBuilder = new JcaContentSignerBuilder("SHA256withRSA");// 签名算法
ContentSigner signer = null;
signer = csBuilder.build(gen.getPrivateKey());
PKCS10CertificationRequest csr = p10Builder.build(signer);// PKCS10的请求
return csr;//返回PKCS10的请求
CA接受请求并生成证书
CertificateFactory certFactory = CertificateFactory.getInstance("X.509");
X509Certificate cacert = (X509Certificate) certFactory.generateCertificate(new FileInputStream(certPath));
//一大堆参数 ,填充到生成器里
AlgorithmIdentifier sigAlgId = new DefaultSignatureAlgorithmIdentifierFinder().find("SHA1withRSA");
AlgorithmIdentifier digAlgId = new DefaultDigestAlgorithmIdentifierFinder().find(sigAlgId);
org.bouncycastle.asn1.x500.X500Name issuer = new org.bouncycastle.asn1.x500.X500Name(
cacert.getSubjectX500Principal().getName());
BigInteger serial = new BigInteger(32, new SecureRandom());
Date from = new Date();
Date to = new Date(System.currentTimeMillis() + (365 * 80 * 86400000L));
X509v3CertificateBuilder certgen = new X509v3CertificateBuilder(issuer, serial, from, to, csr.getSubject(),
csr.getSubjectPublicKeyInfo())
Key privateKey = productPrivateKey();
// CA端进行签名, 才有具有法律效力
ContentSigner signer = new BcRSAContentSignerBuilder(sigAlgId, digAlgId)
.build(PrivateKeyFactory.createKey(privateKey.getEncoded()));
// 生成BC结构的证书
Security.addProvider(new BouncyCastleProvider());
X509Certificate resultBc = new JcaX509CertificateConverter().setProvider("BC").getCertificate(certgen.build(signer));
return resultBc;//返回证书
CSR：证书签发请求(Certificate Signing Request)，
CSR也叫做认证申请，是一个发送到CA的请求认证信息。 有两种格式，应用最广泛的是由PKCS#10定义的，另一个用的少的是由SPKAC定义的，主要应用于网景浏览器。
在PKCS#10定义中，CSR有两种编码格式：二进制(ASN.1或DER (Distinguished Encoding Rules))和文本格式(the text or PEM (Privacy Enhanced Mail)formatted CSR is the binary CSR after it has been Base-64 encoded to create a text version of the CSR.)
CSR文件生成步骤如下：
根据Version、Distinguished Name、Public Key、Attributes生成请求证书；
用Private Key加密证书请求信息；
根据请求信息、签名算法和签名生成CSR文件；
CSR文件包含的信息描述如下
CertificationRequest ::= SEQUENCE {
certificationRequestInfo CertificationRequestInfo,//证书信息
signatureAlgorithm AlgorithmIdentifier{{ SignatureAlgorithms }},//签名算法
signature BIT STRING //签名
}//另外还可能有可选的字段，如postal address和Email address，这两个字段可以应用于证书的撤销。
注意：私钥不包含在CSR文件中，但是应用于数字签名。
签名分两步
将certificateRequestInfo 进行DER编码，产生八位字节字符串；
将步骤一的结果用请求者的私钥在指定的签名算法下，产生签名；
请求信息定义如下
CertificationRequestInfo ::= SEQUENCE {
version INTEGER { v1(0) } (v1,...),
subject Name, //证书主体的专有名称
subjectPKInfo SubjectPublicKeyInfo{{ PKInfoAlgorithms }},
attributes [0] Attributes{{ CRIAttributes }}
}
subjectPublicKeyInfo 包含被认证的公钥
attributes 关于认证主提其他信息属性集合
SubjectPublicKeyInfo { ALGORITHM : IOSet} ::= SEQUENCE {
algorithm AlgorithmIdentifier {{IOSet}},
subjectPublicKey BIT STRING
}
PKInfoAlgorithms ALGORITHM ::= {
... -- add any locally defined algorithms here -- }
Attributes { ATTRIBUTE:IOSet } ::= SET OF Attribute{{ IOSet }}
CRIAttributes ATTRIBUTE ::= {
... -- add any locally defined attributes here -- }
Attribute { ATTRIBUTE:IOSet } ::= SEQUENCE {
type ATTRIBUTE.&id({IOSet}),
values SET SIZE(1..MAX) OF ATTRIBUTE.&Type({IOSet}{@type})
}
等价写法
CertificationRequest ::= SIGNED { EncodedCertificationRequestInfo }
(CONSTRAINED BY { -- Verify or sign encoded
-- CertificationRequestInfo -- })
EncodedCertificationRequestInfo ::=
TYPE-IDENTIFIER.&Type(CertificationRequestInfo)
SIGNED { ToBeSigned } ::= SEQUENCE {
toBeSigned ToBeSigned,
algorithm AlgorithmIdentifier { {SignatureAlgorithms} },
signature BIT STRING
}