OpenSSL RSA Key的生成和转换

1. RSA Key的生成


生成2048 bit的私钥

$ openssl genrsa -out Key0.pem -f4 2048Generating RSA private key, 2048 bit long modulus....................................+++.................................+++e is 65537 (0x10001)

$ cat Key0.pem 

-----BEGIN RSA PRIVATE KEY-----MIIEowIBAAKCAQEA1IJ2tHYgAQ9/SbGPgc/pgAq/gfcp/HsOpJyQgOTBMWbD6CBz

BJh4FzxP+RuJflOm7ILXc3QOO+ccJIT/6P8yuRp4JgWnd8r5wvAwBCzYrRV8zz6Y

tgbBO7ORtd/lPtHzdLXj52/aAbrRu4L8qu3C8acOrM6EjY6nKUdtbYRhm2VssSE5

ApU3pPKW6/QYXrUGypj8E8pujtYbtQIir4OXpMzJ2+AYeZOvjqSTuDSvet2As3qj

BdpBTXWfNC44FHAolcWI6U8Q/L6QKO2H8P11IZAA8aHZva2vudcxVwKz2QiOR1yV

ey4iXk2BhbOJQxC0XT3cc8k7Pbr+BHCDjR7i8wIDAQABAoIBAQCHlsJUfDYJVzD4

/SC6S8UJHFJ6gxA39vAt2XNduhcGBTKkLegVG48sDCBeqdI9VvRfXVBIatkWIWxU

ZMO/jux3LEtSvzLN/SUE2ylX0KFjNh2PQbpAEelCxV0H9VYYke7LHa7PIQ+xINjm0jmSeedzNgrn+VCb3VQMw3UvdlKsyYx6j2AKx4qmML2T6qhwn/racKqTArH/9I2h

y47cxZYYACWwMD4R4NVj/UVy1yc4JU0HrtgyIo9fZL2CpGx/ZxQ0fKBGa5pI3xmn

TZZzbTUy3SGORijr1R5dYe48ZnxYc7n4G7/E9aiytrvDuny3b4crPu2UAyqsDfBK

j8ercULpAoGBAPqeKEC9J+hMGy4U1Ssu5ZqaNXxvLUEfT/ge+s/iVdh/dCtYEeqh

iR8MFJ7cqGUZt/ecR9remF/xGdXob0YssfaZiBEYu8mgr5mR4/xhF15fJHTmuyla

K3xsjOpMYTcF5KGQdwNnIXfodgL58xbel0ksx70qS/OOH60XF30Oe5KFAoGBANkS

y79dRokQDVqMDIPNswfxA7kFteL6wgXXnVgTqTCDZm7L3TnTBxwj5ZETxUm0RuA/FdY46L54eiWcOpHcdMlKyf4Re9H855/25bUQf28e7LLRciuGUCZxNRKQ6r3IIERi

q0/9q5Hdec81kWOL7i8O8qeyP3wC1yiXSynM0aUXAoGAW3i+WGKx3idpBDi2VTyY

sQT34KLzcYFsPrOP97A0hQB/9hH++BRdZ+eQ3yrKi5wHeWihEVGNa/cj5t8fPg2y

Jr+C2jqcz8rGTNbiz4rgbKFtPP258i3nEVLNW/bkxKByAkYoKiXKIWnHKO7xurcj

oKGnhXOapRqKlTKIcCyJDcECgYAUGGRaQ9VKzPyffEWQUhOX0Z0JnNi4uYQKrGo5

hCBuiEuMSD0jpECNP1l6M71Y1GKXUd/ApCYPs/GC19KoPCNnmw/WAGJZDzOWIHIl

b/CMJe29pBwQoW98D5DdNiM1DHjIO+YmEpK2fy1OnGPoNkUHgDfAhITSAyVN8auY

pAhoYwKBgAMHL7a52J2oI1gM5lKA+odLXIIScm4TC3CCqkcVajrY3XbCqVz+oRFK

gzZoGIYOpBaYD/zy8vdL5Ds4Tg0ueo4yTyqnmSG34ydNabTnVyyj6z0W1Q/nhnJ8

KiYJx4ZGR1/xLWfk0XDQmKEwwU2jDUN/++nm5XXVkUI6tHKOvhf4-----END RSA PRIVATE KEY-----123456789101112131415161718192021222324252627282930313233

由于-inform和-outform的默认参数为PEM,所以这里的完整命令为:


$ openssl genrsa -outform=PEM -out Key0.pem -f4 2048 1

从私钥导出公钥

$ openssl rsa -in Key0.pem -pubout -out Key0_pub.pem

writing RSA key$ cat Key0_pub.pem 

-----BEGIN PUBLIC KEY-----

MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA1IJ2tHYgAQ9/SbGPgc/p

gAq/gfcp/HsOpJyQgOTBMWbD6CBzBJh4FzxP+RuJflOm7ILXc3QOO+ccJIT/6P8y

uRp4JgWnd8r5wvAwBCzYrRV8zz6YtgbBO7ORtd/lPtHzdLXj52/aAbrRu4L8qu3C8acOrM6EjY6nKUdtbYRhm2VssSE5ApU3pPKW6/QYXrUGypj8E8pujtYbtQIir4OX

pMzJ2+AYeZOvjqSTuDSvet2As3qjBdpBTXWfNC44FHAolcWI6U8Q/L6QKO2H8P11

IZAA8aHZva2vudcxVwKz2QiOR1yVey4iXk2BhbOJQxC0XT3cc8k7Pbr+BHCDjR7i8wIDAQAB

-----END PUBLIC KEY-----123456789101112

2. RSA Key的转换


在用openssl rsa命令生成RSA Key时有3种可选格式,分别为PEM,DER和NET,通过-inform参数指定,默认为PEM。 

- DER: 原始的RSA Key按照ASN1 DER编码的方式存储 

- PEM: DER经过base64编码转换为PEM格式 

- NET: OpenSSL的帮助提示显示,NET是一个同老式的Netscape server和微软IIS .key文件兼容的格式(不过我没有详细研究过这种格式)


除了上面提到的3种格式外,最常见的还有可读性较好的文本格式,这里称为TXT格式。以下是PEM,DER和TXT格式之间的相互转换。


2.1 PEM转DER格式


直接通过openssl rsa进行输入格式和输出格式的转换。


# 私钥:PEM --(convert)--> DER$ openssl rsa -inform PEM -in Key0.pem -outform DER -out Key0.der$# 公钥:PEM --(convert)> DER$ openssl rsa -inform PEM -in Key0_pub.pem -pubin -outform DER -out Key0_pub.der12345

既然PEM是DER格式进行base64编码的格式,那PEM通过base64解码应为DER格式:


# 私钥:PEM --(decryption)--> DER$ openssl base64 -d -in Key0.pem -out Key0.bin$# 公钥:PEM --(decryption)--> DER$ openssl base64 -d -in Key0_pub.pem -out Key0_pub.bin12345

比较以上两种方法生成的文件Key0.der和Key0.bin,以及Key0_pub.der和Key0_pub.bin,其md5sum的结果一样,说明内容一样:


$ md5sum Key0.der Key0.bin Key0_pub.der Key0_pub.bin f6fa3ec1e35866578fccd507cb106f08  Key0.derf6fa3ec1e35866578fccd507cb106f08  Key0.binfd15765f1656cc3332992cf6e979217f  Key0_pub.derfd15765f1656cc3332992cf6e979217f  Key0_pub.bin12345

2.2 DER转PEM格式


跟PEM转DER格式一样,可以通过openssl rsa命令和openssl base64命令进行转换。


使用openssl rsa命令转换:


# 私钥:DER --(convert)--> PEM$ openssl rsa -inform DER -in Key0.der -outform PEM -out Key0.PEM $# 公钥:DER --(convert)--> PEM$ openssl rsa -inform DER -in Key0_pub.der -pubin -outform PEM -out Key0_pub.PEM12345

使用openssl base64命令转换:


# 私钥:DER --(encryption)--> PEM$ openssl base64 -e -in Key0.der -out Key0.pem$# 公钥:DER --(encryption)--> PEM$ openssl base64 -e -in Key0_pub.der -out Key0_pub.pem12345

以下是两种转换方式得到的内容,略有不同。


$ cat Key0_pub.PEM

-----BEGIN PUBLIC KEY-----

MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA1IJ2tHYgAQ9/SbGPgc/p

gAq/gfcp/HsOpJyQgOTBMWbD6CBzBJh4FzxP+RuJflOm7ILXc3QOO+ccJIT/6P8y

uRp4JgWnd8r5wvAwBCzYrRV8zz6YtgbBO7ORtd/lPtHzdLXj52/aAbrRu4L8qu3C8acOrM6EjY6nKUdtbYRhm2VssSE5ApU3pPKW6/QYXrUGypj8E8pujtYbtQIir4OX

pMzJ2+AYeZOvjqSTuDSvet2As3qjBdpBTXWfNC44FHAolcWI6U8Q/L6QKO2H8P11

IZAA8aHZva2vudcxVwKz2QiOR1yVey4iXk2BhbOJQxC0XT3cc8k7Pbr+BHCDjR7i8wIDAQAB

-----END PUBLIC KEY-----

$ cat Key0_pub.pem 

MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA1IJ2tHYgAQ9/SbGPgc/p

gAq/gfcp/HsOpJyQgOTBMWbD6CBzBJh4FzxP+RuJflOm7ILXc3QOO+ccJIT/6P8y

uRp4JgWnd8r5wvAwBCzYrRV8zz6YtgbBO7ORtd/lPtHzdLXj52/aAbrRu4L8qu3C8acOrM6EjY6nKUdtbYRhm2VssSE5ApU3pPKW6/QYXrUGypj8E8pujtYbtQIir4OX

pMzJ2+AYeZOvjqSTuDSvet2As3qjBdpBTXWfNC44FHAolcWI6U8Q/L6QKO2H8P11

IZAA8aHZva2vudcxVwKz2QiOR1yVey4iXk2BhbOJQxC0XT3cc8k7Pbr+BHCDjR7i8wIDAQAB123456789101112131415161718

其唯一不同的后者Key0_pub.pem是通过openssl base64命令得到的文件,丢失了”-----BEGIN PUBLIC KEY-----“和”-----END PUBLIC KEY-----“这两条注释信息。


2.3 PEM转TXT格式


直接通过openssl rsa命令的-text参数输出可读的TXT格式:


# 私钥:PEM --> TXT$ openssl rsa -inform PEM -in Key0.PEM -text -out Key0.txt$# 公钥:PEM --> TXT$ openssl rsa -inform PEM -in Key0_pub.PEM -pubin -text -out Key0_pub.txt12345

实践发现,转换为TXT的PEM文件需要包含”-----BEGIN PUBLIC KEY-----“和”-----END PUBLIC KEY-----“标记,没有这个标记转换会失败。 

例如,以下将DER通过openssl base64命令加密为PEM格式后,再尝试转换为TXT格式失败。


$ openssl rsa -inform PEM -in Key0.pem -text -out Key0.txt

unable to load Private Key140185959843488:error:0906D06C:PEM routines:PEM_read_bio:no start line:pem_lib.c:703:Expecting: ANY PRIVATE KEY

$ cat Key0.pem

MIIEowIBAAKCAQEA1IJ2tHYgAQ9/SbGPgc/pgAq/gfcp/HsOpJyQgOTBMWbD6CBz

BJh4FzxP+RuJflOm7ILXc3QOO+ccJIT/6P8yuRp4JgWnd8r5wvAwBCzYrRV8zz6Y

tgbBO7ORtd/lPtHzdLXj52/aAbrRu4L8qu3C8acOrM6EjY6nKUdtbYRhm2VssSE5

ApU3pPKW6/QYXrUGypj8E8pujtYbtQIir4OXpMzJ2+AYeZOvjqSTuDSvet2As3qj

BdpBTXWfNC44FHAolcWI6U8Q/L6QKO2H8P11IZAA8aHZva2vudcxVwKz2QiOR1yV

ey4iXk2BhbOJQxC0XT3cc8k7Pbr+BHCDjR7i8wIDAQABAoIBAQCHlsJUfDYJVzD4

/SC6S8UJHFJ6gxA39vAt2XNduhcGBTKkLegVG48sDCBeqdI9VvRfXVBIatkWIWxU

ZMO/jux3LEtSvzLN/SUE2ylX0KFjNh2PQbpAEelCxV0H9VYYke7LHa7PIQ+xINjm

0jmSeedzNgrn+VCb3VQMw3UvdlKsyYx6j2AKx4qmML2T6qhwn/racKqTArH/9I2h

y47cxZYYACWwMD4R4NVj/UVy1yc4JU0HrtgyIo9fZL2CpGx/ZxQ0fKBGa5pI3xmn

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K3xsjOpMYTcF5KGQdwNnIXfodgL58xbel0ksx70qS/OOH60XF30Oe5KFAoGBANkS

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FdY46L54eiWcOpHcdMlKyf4Re9H855/25bUQf28e7LLRciuGUCZxNRKQ6r3IIERiq0/9q5Hdec81kWOL7i8O8qeyP3wC1yiXSynM0aUXAoGAW3i+WGKx3idpBDi2VTyY

sQT34KLzcYFsPrOP97A0hQB/9hH++BRdZ+eQ3yrKi5wHeWihEVGNa/cj5t8fPg2y

Jr+C2jqcz8rGTNbiz4rgbKFtPP258i3nEVLNW/bkxKByAkYoKiXKIWnHKO7xurcj

oKGnhXOapRqKlTKIcCyJDcECgYAUGGRaQ9VKzPyffEWQUhOX0Z0JnNi4uYQKrGo5

hCBuiEuMSD0jpECNP1l6M71Y1GKXUd/ApCYPs/GC19KoPCNnmw/WAGJZDzOWIHIl

b/CMJe29pBwQoW98D5DdNiM1DHjIO+YmEpK2fy1OnGPoNkUHgDfAhITSAyVN8auY

pAhoYwKBgAMHL7a52J2oI1gM5lKA+odLXIIScm4TC3CCqkcVajrY3XbCqVz+oRFK

gzZoGIYOpBaYD/zy8vdL5Ds4Tg0ueo4yTyqnmSG34ydNabTnVyyj6z0W1Q/nhnJ8

KiYJx4ZGR1/xLWfk0XDQmKEwwU2jDUN/++nm5XXVkUI6tHKOvhf41234567891011121314151617181920212223242526272829

对比这里的key0.pem可最初生成的内容,唯一的差别就是这里缺少”-----BEGIN PUBLIC KEY-----“和”-----END PUBLIC KEY-----“标记


2.4 TXT转PEM格式


我不知道如何用openssl命令进行转换,谁知道的告诉我啊~~~


但是,我相信看过TXT内容的都应该知道如何进行转换,因为TXT文件最后的”-----BEGIN PUBLIC KEY-----“和”-----END PUBLIC KEY-----“部分就是PEM内容。





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