OpenSSL的RSA私鑰和公鑰

Question

如果我使用開放SSL命令

sudo openssl genrsa -out privkey.pem 2048 

產生RSA密鑰，只生成1個文件。這是私鑰。我如何獲得公鑰？

Answer 1

要回答您的問題：您使用sudo openssl genrsa -out privkey.pem 2048生成的文件包含私鑰和公鑰。

openssl genrsagenerates a key pair。公鑰是模量（N）和公開指數（e）：

$ openssl genrsa 2048 > dummy.key 
$ openssl rsa -in dummy.key -noout -text 

Private-Key: (2048 bit) 
modulus: 
    00:d4:4a:3c:8c:41:b3:9b:a3:26:2d:4b:8c:62:08: 
    c0:fc:ad:6c:5e:5f:3f:28:e6:a3:7c:3d:43:5e:98: 
    [...] 
publicExponent: 65537 (0x10001) 
privateExponent: 
    00:c7:6e:f6:72:cd:46:6e:70:56:ed:36:8c:2b:8d: 
    0d:c0:53:2b:fb:7c:7f:59:6d:53:28:e4:64:e5:f9: 
    d6:84:64:7e:e4:be:20:64:7d:5b:50:06:ba:1f:df: 
    [...] 

可以使用-pubout選項openssl rsa只提取公鑰：

$ openssl rsa -in dummy.key -pubout 
writing RSA key 
-----BEGIN PUBLIC KEY----- 
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA1Eo8jEGzm6MmLUuMYgjA 
[...] 
gW6qhadXVsKWQhEhVU9s7V9vJOhfeSSahvuZR0zjursTm6PSJWo7lKNgFCFC0NXO 
LQIDAQAB 
-----END PUBLIC KEY----- 

如果您將該數據提取到文件中並重新讀取它，您將看到它包含模數和指數：

$ openssl rsa -in dummy.key -pubout > public.key 
$ openssl rsa -in public.key -pubin -noout -text 
Public-Key: (2048 bit) 
Modulus: 
    00:d4:4a:3c:8c:41:b3:9b:a3:26:2d:4b:8c:62:08: 
    c0:fc:ad:6c:5e:5f:3f:28:e6:a3:7c:3d:43:5e:98: 
    [...] 
    6f:24:e8:5f:79:24:9a:86:fb:99:47:4c:e3:ba:bb: 
    13:9b:a3:d2:25:6a:3b:94:a3:60:14:21:42:d0:d5: 
    ce:2d 
Exponent: 65537 (0x10001) 
$