目录

• 前言
• 引入依赖
• 一、公钥转换
• • 公钥PKCS1转PKCS8
  • 公钥PKCS8转PKCS1
• 二、私钥转换
• • 私钥PKCS1转PKCS8
  • 私钥PKCS8转PKCS1
• 三、公钥还原
• • 公钥byte数组还原为PKCS1 java对象
  • 公钥byte数组还原为PKCS8 java对象
• 四、私钥还原
• • 私钥byte数组还原为PKCS1 java对象
  • 私钥byte数组还原为PKCS8 java对象
• 五、调用示例
• 完整代码，包括RSA加解密、签名验签
• 总结

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前言

项目中底层生成的公私钥都是pkcs1格式的，但是java中使用的都是pkcs8的，需要转换。在网上找了很多方法， 但都不是很全面。并且网上大部分方法已经被标为过时了，写在代码里全是横线，看着很不舒服。如图中的RSAPrivateKeyStructure类已经不推荐使用，网上大部分还是用这种方式。
因此结合两种标准的格式规定和bouncycastle的源码，自己写了以下的方法。

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引入依赖

依赖bcprov-jdk15on包，以下方法均出自这个包。本人使用的1.51版本，亲测可行。
方法一：

<dependency><groupId>org.bouncycastle</groupId><artifactId>bcprov-jdk15on</artifactId><version>1.51</version></dependency>

或引入下面的包，会自动引入上面的bcprov-jdk15on包
方法二：

<dependency><groupId>org.bouncycastle</groupId><artifactId>bcpkix-jdk15on</artifactId><version>1.51</version></dependency>

因项目中使用了bcpkix-jdk15on包中的方法，所以需要两个包都引入，采用第二种方法引入。

导入的类

import org.bouncycastle.asn1.ASN1Encodable; import org.bouncycastle.asn1.ASN1Sequence; import org.bouncycastle.asn1.DERBitString; import org.bouncycastle.asn1.pkcs.PKCSObjectIdentifiers; import org.bouncycastle.asn1.pkcs.PrivateKeyInfo; import org.bouncycastle.asn1.pkcs.RSAPrivateKey; import org.bouncycastle.asn1.pkcs.RSAPublicKey; import org.bouncycastle.asn1.x509.AlgorithmIdentifier;

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一、公钥转换

公钥PKCS1转PKCS8

public static byte[] formatPublicKeyPKCS1ToPKCS8(byte[] pkcs1PublicKeyByte) {RSAPublicKey rsaPub = RSAPublicKey.getInstance(pkcs1PublicKeyByte);byte[] pkcs8Bytes = null;try {KeyFactory kf = KeyFactory.getInstance("RSA");PublicKey generatePublic = kf.generatePublic(new RSAPublicKeySpec(rsaPub.getModulus(), rsaPub.getPublicExponent()));pkcs8Bytes = generatePublic.getEncoded();} catch (NoSuchAlgorithmException e) {e.printStackTrace();} catch (InvalidKeySpecException e) {e.printStackTrace();}return pkcs8Bytes;}

公钥PKCS8转PKCS1

public static byte[] formatPublicKeyPKCS8ToPKCS1(byte[] pkcs8PublicKeyByte) {ASN1Sequence publicKeyASN1Object = ASN1Sequence.getInstance(pkcs8PublicKeyByte);ASN1Encodable derBitStringASN1Encodable = publicKeyASN1Object.getObjectAt(1);DERBitString derBitStringObject = DERBitString.getInstance(derBitStringASN1Encodable);return derBitStringObject.getBytes();}

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二、私钥转换

私钥PKCS1转PKCS8

public static byte[] formatPrivateKeyPKCS1ToPKCS8(byte[] pkcs1PrivateKeyByte) {AlgorithmIdentifier algorithmIdentifier = new AlgorithmIdentifier(PKCSObjectIdentifiers.pkcs8ShroudedKeyBag); RSAPrivateKey privateKey = RSAPrivateKey.getInstance(pkcs1PrivateKeyByte);//另一种方式//ASN1Sequence privateKey = ASN1Sequence.getInstance(pkcs1PrivateKeyByte);byte[] pkcs8Bytes = null;try {PrivateKeyInfo privKeyInfo = new PrivateKeyInfo(algorithmIdentifier, privateKey); pkcs8Bytes = privKeyInfo.getEncoded();} catch (IOException e) {e.printStackTrace();}return pkcs8Bytes;}

私钥PKCS8转PKCS1

方法一

public static byte[] formatPrivateKeyPKCS8ToPKCS1(byte[] pksc8PrivateKeyByte) {PrivateKeyInfo pki = PrivateKeyInfo.getInstance(pksc8PrivateKeyByte);byte[] pkcs1Bytes = null;try {ASN1Encodable parsePrivateKey = pki.parsePrivateKey();pkcs1Bytes = parsePrivateKey.toASN1Primitive().getEncoded();} catch (IOException e) {e.printStackTrace();}return pkcs1Bytes;}

方法二

public static byte[] formatPrivateKeyPKCS8ToPKCS1(byte[] pksc8PrivateKeyByte) {PrivateKeyInfo pki = PrivateKeyInfo.getInstance(pksc8PrivateKeyByte);byte[] pkcs1Bytes = null;try {RSAPrivateKey parsePrivateKey = RSAPrivateKey.getInstance(pki.parsePrivateKey());pkcs1Bytes = parsePrivateKey.getEncoded();} catch (IOException e) {e.printStackTrace();}return pkcs1Bytes;}

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三、公钥还原

公钥byte数组还原为PKCS1 java对象

方法一（推荐）

public static RSAPublicKey formatPKCS1PublicKey(byte[] pkcs1PublicKeyByte) {RSAPublicKey publicKey = RSAPublicKey.getInstance(pkcs1PublicKeyByte);return publicKey;}

方法二

public static ASN1Encodable formatPKCS1PublicKey(byte[] pkcs1PublicKeyByte) {ASN1Sequence publicKey = ASN1Sequence.getInstance(pkcs1PublicKeyByte);return publicKey;}

公钥byte数组还原为PKCS8 java对象

public static PublicKey formatPKCS8PublicKey(byte[] pkcs8PublicKeyByte) {PublicKey publicKey = null;EncodedKeySpec keySpec = new X509EncodedKeySpec(pkcs8PublicKeyByte);try {KeyFactory keyFactory = KeyFactory.getInstance("RSA");publicKey = keyFactory.generatePublic(keySpec);} catch (NoSuchAlgorithmException e) {e.printStackTrace();} catch (InvalidKeySpecException e) {e.printStackTrace();}return publicKey;}

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四、私钥还原

私钥byte数组还原为PKCS1 java对象

方法一（推荐）

public static RSAPrivateKey formatPKCS1PrivateKey(byte[] pkcs1PrivateKeyByte) {RSAPrivateKey privateKey = RSAPrivateKey.getInstance(pkcs1PrivateKeyByte);return privateKey;}

方法二

public static ASN1Encodable formatPKCS1PrivateKey_2(byte[] pkcs1PrivateKeyByte) {ASN1Sequence privateKey = ASN1Sequence.getInstance(pkcs1PrivateKeyByte);return privateKey;}

私钥byte数组还原为PKCS8 java对象

public static PrivateKey formatPKCS8PrivateKey(byte[] pkcs8PrivateKeyByte) {PrivateKey privateKey = null;EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(pkcs8PrivateKeyByte);try {KeyFactory keyFactory = KeyFactory.getInstance("RSA");privateKey = keyFactory.generatePrivate(keySpec);} catch (NoSuchAlgorithmException e) {e.printStackTrace();} catch (InvalidKeySpecException e) {e.printStackTrace();}return privateKey;}

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五、调用示例

static byte[] pkcs1PrivateKeyByte=Base64.decode("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");static byte[] pkcs1PublicKeyByte=Base64.decode("MIGJAoGBAL8i/l5stLZChT8XzyNK+tOkzGHRLd8oXL39U691qxncGuj6x/qRT/9YjlyuqJ2JADibY3FyQwdRz8VQ9rMBC2j9s8kNVqCT2sH5RqFNnqDPF9NrgaSkzeNNcCmkl+Wz1C7UjMstegqCxP3XBh2bbV7X/ii2ZqBNhrmnACLB8AIRAgMBAAE=");public static void getKeyPair() {//pkcs1公钥转pkcs8 pkcs8公钥还原PublicKey publicKey2 = formatPKCS8PublicKey(formatPublicKeyPKCS1ToPKCS8(pkcs1PublicKeyByte));//pkcs1私钥转pkcs8 pkcs8私钥还原PrivateKey privateKey2 = formatPKCS8PrivateKey(formatPrivateKeyPKCS1ToPKCS8(pkcs1PrivateKeyByte));//pkcs8私钥转pkcs1 pkcs1私钥还原formatPKCS1PrivateKey(formatPrivateKeyPKCS8ToPKCS1(privateKey2.getEncoded()));//pkcs8公钥转pkcs1 pkcs1公钥还原formatPKCS1PublicKey(formatPublicKeyPKCS8ToPKCS1(publicKey2.getEncoded()));}

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完整代码，包括RSA加解密、签名验签

package com.CryptTest;import java.io.ByteArrayOutputStream; import java.io.IOException; import java.security.InvalidKeyException; import java.security.KeyFactory; import java.security.KeyPair; import java.security.KeyPairGenerator; import java.security.NoSuchAlgorithmException; import java.security.PrivateKey; import java.security.PublicKey; import java.security.SignatureException; import java.security.spec.EncodedKeySpec; import java.security.spec.InvalidKeySpecException; import java.security.spec.PKCS8EncodedKeySpec; import java.security.spec.RSAPublicKeySpec; import java.security.spec.X509EncodedKeySpec;import javax.crypto.BadPaddingException; import javax.crypto.Cipher; import javax.crypto.IllegalBlockSizeException; import javax.crypto.NoSuchPaddingException;import org.bouncycastle.asn1.ASN1Encodable; import org.bouncycastle.asn1.ASN1Sequence; import org.bouncycastle.asn1.DERBitString; import org.bouncycastle.asn1.pkcs.PKCSObjectIdentifiers; import org.bouncycastle.asn1.pkcs.PrivateKeyInfo; import org.bouncycastle.asn1.pkcs.RSAPrivateKey; import org.bouncycastle.asn1.pkcs.RSAPrivateKeyStructure; import org.bouncycastle.asn1.pkcs.RSAPublicKey; import org.bouncycastle.asn1.x509.AlgorithmIdentifier;import cn.hutool.core.codec.Base64; import sun.misc.BASE64Decoder; import sun.misc.BASE64Encoder;/*** RSA算法实现过程为：1. 随意选择两个大的质数p和q，p不等于q，计算N=pq。2. 根据欧拉函数，不大于N且与N互质的整数個数為(p-1)(q-1)。3. 选择一个整数e与(p-1)(q-1)互质，并且e小于(p-1)(q-1)。4. 用以下这个公式计算d：d× e ≡ 1 (mod (p-1)(q-1))。5. 将p和q的记录销毁。以上内容中，(N,e)是公钥，(N,d)是私钥。* @author Administrator**/ public class RSADemo {/** *//** * RSA最大加密明文大小 */ private static final int MAX_ENCRYPT_BLOCK = 117; static byte[] pkcs1PrivateKeyByte=Base64.decode("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");static byte[] pkcs1PublicKeyByte=Base64.decode("MIGJAoGBAL8i/l5stLZChT8XzyNK+tOkzGHRLd8oXL39U691qxncGuj6x/qRT/9YjlyuqJ2JADibY3FyQwdRz8VQ9rMBC2j9s8kNVqCT2sH5RqFNnqDPF9NrgaSkzeNNcCmkl+Wz1C7UjMstegqCxP3XBh2bbV7X/ii2ZqBNhrmnACLB8AIRAgMBAAE=");private PublicKey publicKey;private PrivateKey privateKey;public static void main(String[] args) {signTest();getKeyPair();}public static void signTest() {RSADemo rsa=new RSADemo();byte[] data="123".getBytes();//加密 此处用公钥加密 也可以反过来 用私钥加密 用公钥解密byte []eData=rsa.encryptData(data, rsa.publicKey);String eDataEncode=new BASE64Encoder().encode(eData);System.out.println("加密后: "+eDataEncode);//解密try {byte[] dData=rsa.decryptData(new BASE64Decoder().decodeBuffer(eDataEncode), rsa.privateKey);System.out.println("解密后: "+new String(dData));} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}String SIGN_sha256 = "SHA256WithRSA"; String SIGN_sh1 = "SHA1WithRSA"; String sign = rsa.sign(data,SIGN_sha256);String sign2 = rsa.sign(data,SIGN_sh1);//签名System.out.println(SIGN_sha256+"签名:"+sign);System.out.println(SIGN_sh1+" 签名:"+sign2);boolean verify = rsa.verify(data,sign,SIGN_sha256);boolean verify2 = rsa.verify(data,sign2,SIGN_sh1);System.out.println(SIGN_sha256+"验签:"+verify);System.out.println(SIGN_sh1+"验签:"+verify2);}public static void getKeyPair() {//通过byte[]可以再度将公钥或私钥还原出来PublicKey publicKey2 = formatPKCS8PublicKey(formatPublicKeyPKCS1ToPKCS8(pkcs1PublicKeyByte));PrivateKey privateKey2 = formatPKCS8PrivateKey(formatPrivateKeyPKCS1ToPKCS8(pkcs1PrivateKeyByte));RSAPrivateKey formatPKCS1PrivateKey = formatPKCS1PrivateKey(formatPrivateKeyPKCS8ToPKCS1(privateKey2.getEncoded()));RSAPrivateKey formatPKCS1PrivateKey_2 = formatPKCS1PrivateKey(formatPrivateKeyPKCS8ToPKCS1_2(privateKey2.getEncoded()));ASN1Encodable formatPKCS1PrivateKey_2_2 = formatPKCS1PrivateKey_2(formatPrivateKeyPKCS8ToPKCS1_2(privateKey2.getEncoded()));RSAPublicKey formatPKCS1PublicKey = formatPKCS1PublicKey(formatPublicKeyPKCS8ToPKCS1(publicKey2.getEncoded()));ASN1Encodable formatPKCS1PublicKey_2 = formatPKCS1PublicKey_2(formatPublicKeyPKCS8ToPKCS1(publicKey2.getEncoded()));}public static byte[] formatPrivateKeyPKCS1ToPKCS8(byte[] pkcs1PrivateKeyByte) {AlgorithmIdentifier algorithmIdentifier = new AlgorithmIdentifier(PKCSObjectIdentifiers.pkcs8ShroudedKeyBag); RSAPrivateKey privateKey = RSAPrivateKey.getInstance(pkcs1PrivateKeyByte);//另一种方式ASN1Sequence privateKey1 = ASN1Sequence.getInstance(pkcs1PrivateKeyByte);byte[] pkcs8Bytes = null;try {PrivateKeyInfo privKeyInfo = new PrivateKeyInfo(algorithmIdentifier, privateKey); PrivateKeyInfo privKeyInfo1 = new PrivateKeyInfo(algorithmIdentifier, privateKey1); pkcs8Bytes = privKeyInfo.getEncoded();} catch (IOException e) {e.printStackTrace();}return pkcs8Bytes;}public static byte[] formatPrivateKeyPKCS8ToPKCS1(byte[] pksc8PrivateKeyByte) {PrivateKeyInfo pki = PrivateKeyInfo.getInstance(pksc8PrivateKeyByte);byte[] pkcs1Bytes = null;try {ASN1Encodable parsePrivateKey = pki.parsePrivateKey();pkcs1Bytes = parsePrivateKey.toASN1Primitive().getEncoded();} catch (IOException e) {e.printStackTrace();}return pkcs1Bytes;}public static byte[] formatPrivateKeyPKCS8ToPKCS1_2(byte[] pksc8PrivateKeyByte) {PrivateKeyInfo pki = PrivateKeyInfo.getInstance(pksc8PrivateKeyByte);byte[] pkcs1Bytes = null;try {RSAPrivateKey parsePrivateKey = RSAPrivateKey.getInstance(pki.parsePrivateKey());pkcs1Bytes = parsePrivateKey.getEncoded();} catch (IOException e) {e.printStackTrace();}return pkcs1Bytes;}public static byte[] formatPublicKeyPKCS1ToPKCS8(byte[] pkcs1PublicKeyByte) {RSAPublicKey rsaPub = RSAPublicKey.getInstance(pkcs1PublicKeyByte);byte[] pkcs8Bytes = null;try {KeyFactory kf = KeyFactory.getInstance("RSA");PublicKey generatePublic = kf.generatePublic(new RSAPublicKeySpec(rsaPub.getModulus(), rsaPub.getPublicExponent()));pkcs8Bytes = generatePublic.getEncoded();} catch (NoSuchAlgorithmException e) {e.printStackTrace();} catch (InvalidKeySpecException e) {e.printStackTrace();}return pkcs8Bytes;}public static RSAPrivateKeyStructure formatPkcs8ToPkcs1(String rawKey) throws Exception {PrivateKeyInfo pki = PrivateKeyInfo.getInstance(pkcs1PrivateKeyByte);RSAPrivateKeyStructure pkcs1Key = RSAPrivateKeyStructure.getInstance(pki.getPrivateKey());return pkcs1Key;}public static byte[] formatPublicKeyPKCS8ToPKCS1(byte[] pkcs8PublicKeyByte) {ASN1Sequence publicKeyASN1Object = ASN1Sequence.getInstance(pkcs8PublicKeyByte);ASN1Encodable derBitStringASN1Encodable = publicKeyASN1Object.getObjectAt(1);DERBitString derBitStringObject = DERBitString.getInstance(derBitStringASN1Encodable);return derBitStringObject.getBytes();}public static RSAPublicKey formatPKCS1PublicKey(byte[] pkcs1PublicKeyByte) {RSAPublicKey publicKey = RSAPublicKey.getInstance(pkcs1PublicKeyByte);return publicKey;}public static ASN1Encodable formatPKCS1PublicKey_2(byte[] pkcs1PublicKeyByte) {ASN1Sequence publicKey = ASN1Sequence.getInstance(pkcs1PublicKeyByte);return publicKey;}public static RSAPrivateKey formatPKCS1PrivateKey(byte[] pkcs1PrivateKeyByte) {RSAPrivateKey privateKey = RSAPrivateKey.getInstance(pkcs1PrivateKeyByte);return privateKey;}public static ASN1Encodable formatPKCS1PrivateKey_2(byte[] pkcs1PrivateKeyByte) {ASN1Sequence privateKey = ASN1Sequence.getInstance(pkcs1PrivateKeyByte);return privateKey;}public RSADemo() {try {KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");keyPairGen.initialize(1024);// 密钥位数// 动态生成密钥对KeyPair keyPair = keyPairGen.generateKeyPair();// 公钥publicKey = keyPair.getPublic();// 私钥privateKey = keyPair.getPrivate();//获得公钥私钥的比特编码byte[] publicKeyByte=publicKey.getEncoded();byte[] privateKeyByte=privateKey.getEncoded();//通过byte[]可以再度将公钥或私钥还原出来formatPKCS8PublicKey(publicKeyByte);formatPKCS8PrivateKey(privateKeyByte);} catch (NoSuchAlgorithmException e) {// TODO Auto-generated catch blocke.printStackTrace();}}/*** 用公钥加密* @param publicKey* @return */public byte[] encryptData(byte[] data,PublicKey publicKey) {try {Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");// 加密前设定加密方式及密钥cipher.init(Cipher.ENCRYPT_MODE, publicKey);// 传入编码数据并返回编码结果int inputLen = data.length; ByteArrayOutputStream out = new ByteArrayOutputStream(); int offSet = 0; byte[] cache; int i = 0; // 对数据分段加密 while (inputLen - offSet > 0) { if (inputLen - offSet > MAX_ENCRYPT_BLOCK) { cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK); } else { cache = cipher.doFinal(data, offSet, inputLen - offSet); } out.write(cache, 0, cache.length); i++; offSet = i * MAX_ENCRYPT_BLOCK; } byte[] encryptedData = out.toByteArray(); out.close(); //不分段加密//encryptedData=cipher.doFinal(data);return encryptedData; } catch (InvalidKeyException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (IllegalBlockSizeException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (BadPaddingException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (NoSuchAlgorithmException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (NoSuchPaddingException e) {// TODO Auto-generated catch blocke.printStackTrace();}return null;}/*** 用私钥解密** @param encryptedData 经过encryptedData()加密返回的byte数据* @param privateKey 私钥* @return*/public byte[] decryptData(byte[] encryptedData, PrivateKey privateKey){try{Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");cipher.init(Cipher.DECRYPT_MODE, privateKey);return cipher.doFinal(encryptedData);} catch (Exception e){ e.printStackTrace();return null;}}/*** 通过公钥byte[]将公钥还原，适用于RSA算法* @param pkcs8PublicKeyByte* @return*/public static PublicKey formatPKCS8PublicKey(byte[] pkcs8PublicKeyByte) {PublicKey publicKey = null;EncodedKeySpec keySpec = new X509EncodedKeySpec(pkcs8PublicKeyByte);try {KeyFactory keyFactory = KeyFactory.getInstance("RSA");publicKey = keyFactory.generatePublic(keySpec);} catch (NoSuchAlgorithmException e) {e.printStackTrace();} catch (InvalidKeySpecException e) {e.printStackTrace();}return publicKey;}/*** 通过私钥byte[]将公钥还原，适用于RSA算法* @param pkcs8PrivateKeyByte* @return*/public static PrivateKey formatPKCS8PrivateKey(byte[] pkcs8PrivateKeyByte) {PrivateKey privateKey = null;EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(pkcs8PrivateKeyByte);try {KeyFactory keyFactory = KeyFactory.getInstance("RSA");privateKey = keyFactory.generatePrivate(keySpec);} catch (NoSuchAlgorithmException e) {e.printStackTrace();} catch (InvalidKeySpecException e) {e.printStackTrace();}return privateKey;}public String sign(byte[] data,String SIGN_ALGORITHMS) {try {java.security.Signature signature = java.security.Signature.getInstance(SIGN_ALGORITHMS);signature.initSign(privateKey); signature.update(data);byte[] signed = signature.sign(); return Base64.encode(signed);} catch (InvalidKeyException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (NoSuchAlgorithmException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (SignatureException e) {// TODO Auto-generated catch blocke.printStackTrace();}return null; }public boolean verify(byte[] srcData, String sign,String SIGN_ALGORITHMS) { try { java.security.Signature signature = java.security.Signature .getInstance(SIGN_ALGORITHMS); signature.initVerify(publicKey); signature.update(srcData); boolean bverify = signature.verify( Base64.decode(sign) ); return bverify; } catch (Exception e) { e.printStackTrace(); } return false; } }

总结

以上同一个转换有两种方法的，其实原理都一样。区别在于一个转为标准中规定的结构体，便于获取其中的数据。另一个转为ASN1Encodable，是一个ASN1结构体，同样可以根据数据索引获取其中的数据。

PKCS #1 RSA公钥的ASN.1类型

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

RSAPublic的属性有如下意义：
modulus是RSA的模数n。
publicExponent是RSA的公共指数e。

PKCS #1 RSA私钥的ASN.1类型

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 }

RSAPrivateKey的属性有如下意义：
#version 为了兼容未来的修订提出的版本号。本文的版本，多质数为1，其它则为0.
Version ::= INTEGER { two-prime(0), multi(1) }
(CONSTRAINED BY {-- version must be multi if otherPrimeInfos present --})
# modulus 是RSA模数n
# publicExponent 是RSA公有指数e
# privateExponent 是RSA私有质数d
# prime1 是n的质数因子p
# prime2 是n的质数因子q
# exponent1 是d mod(p-1)
# exponent2 是d mod(q-1)
# coefficient 是CRT系数 q-1 mod p
# otherPrimeInfos 按顺序包含了附加的质数 r3----ru。它在版本0的时候不存在，将包含在版本1中最少一个实例。

OtherPrimeInfos ::= SEQUENCE SIZE(1..MAX) OF OtherPrimeInfo OtherPrimeInfo ::= SEQUENCE { prime INTEGER, -- ri exponent INTEGER, -- di coefficient INTEGER -- ti }

OtherPrimeInfo的属性有如下的含义：
#prime是n的质数因子ri，i>=3.
#exponent是 di = d mod(ri-1)
#coefficient是CRT系数 ti = (r1r2…ri-1) mod ri

PKCS #8 RSA私钥的ASN.1类型

名词解释
pkcs1：PKCS #1 RSA密码编译标准（RSA Cryptography Standard）2.1版本。定义了RSA的数理基础、公/私钥格式，以及加/解密、签/验章的流程。1.5版本曾经遭到攻击。
pkcs8：PKCS #8 私钥消息表示标准（Private-Key Information Syntax Standard） 1.2版本。

总结

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