常用的rsa密钥有两种格式，一种为pkcs1，首尾分别为：
# 公钥 -----BEGIN RSA PUBLIC KEY----- -----END RSA PUBLIC KEY----- # 私钥 -----BEGIN RSA PRIVATE KEY----- -----END RSA PRIVATE KEY-----
另一种为pkcs8，首位分别为：
# 公钥 -----BEGIN PUBLIC KEY----- -----END PUBLIC KEY----- # 私钥 -----BEGIN PRIVATE KEY----- -----END PRIVATE KEY-----
openssl工具生成的公/私钥均为pkcs1格式，而接口请求数据加密用的rsa库使用的格式为pkcs8格式，于是pkcs1格式公私钥与pkcs8格式公私钥的转换成为必须要解决的问题。
http://slproweb.com/products/Win32OpenSSL.html
选择适合自己系统的版本：
RSA私钥格式PKCS1和PKCS8相互转换
RSA公钥格式PKCS1和PKCS8相互转换
以下转换基于openssl命令的操作；
1. openssl 生成pkcs1格式的私钥，密钥长度1024位, (PKCS1)
openssl genrsa -out private.pem 1024
-----BEGIN RSA PRIVATE KEY----- MIICXQIBAAKBgQDlLm5+Kosybacfp8hzjn1fl2wT7Au2lm5SEtz6r+/wwSfq5KfY H8q1AO/C92IwEpplNbrqYmOXQu6P07mg0lQOCvE5sdtmAvD2ex3wCef8lWmgdh5q Uo4OMcmoSz3IAp/7/FnMag1IelSfdronPBDxazp6NUmQZITsYK6CsEl/ewIDAQAB AoGBAJkMdvF+i9Kzc6YqMC0rfQJ3Zs+vFOtsbmQVAMnQ8JWBCJ1O8d/c60wRQgyb lFCyO7VXOmoIJqX/Jr2aER8bFtG+Yxy6jsMu3ynwMwbhcVmCWCmZoWuE5pZdEJk6 lOdOay7TkE45X/Wc7K9iZs2uuB7sylIvK/HVxxit6FGePa4RAkEA9e+VoAbxBv78 HyxRcStW+Kc3lmE4zYBGAb2IYx48UEN34nP5rI8Tusqsy7CZ3rvSMi1CpVlj2eQK FU8FzVFyjwJBAO6PU9q7il8NtecdvYBkDErlCawSeCdk9s79helT0Mrg9cWaVWFO n0UxgT55MPXWGdMRXUUOCNnMilaw/p7dKlUCQDpjGeu3GivmB2dDN0ad2nUIBftu s3SeWoB5RdL6T6liiyi5DfJ4uV9kVKe7Epy9jIabFjJ5SWpmaDps21zGVGMCQQCB HvK0IW3zpOgf/+jh5UUCBJYHnLeMGwm7X11rvQH1zW05Vx9/W565ROI/fjkR1qCD rZJeHgqMWDlIUuR9+BdBAkAI8+JWgWLdWceXX9Puu4KNmGukx4GZw2n53vMKp0Fu puQxMonRWTN+kA76cq8QIj8xuEBkdxy1NFRMEkGu675m -----END RSA PRIVATE KEY-----
2. PKCS1私钥转换为PKCS8
openssl pkcs8 -topk8 -inform PEM -in private.pem -outform pem -nocrypt -out pkcs8.pem
-----BEGIN PRIVATE KEY----- MIICdwIBADANBgkqhkiG9w0BAQEFAASCAmEwggJdAgEAAoGBAOUubn4qizJtpx+n yHOOfV+XbBPsC7aWblIS3Pqv7/DBJ+rkp9gfyrUA78L3YjASmmU1uupiY5dC7o/T uaDSVA4K8Tmx22YC8PZ7HfAJ5/yVaaB2HmpSjg4xyahLPcgCn/v8WcxqDUh6VJ92 uic8EPFrOno1SZBkhOxgroKwSX97AgMBAAECgYEAmQx28X6L0rNzpiowLSt9Andm z68U62xuZBUAydDwlYEInU7x39zrTBFCDJuUULI7tVc6aggmpf8mvZoRHxsW0b5j HLqOwy7fKfAzBuFxWYJYKZmha4Tmll0QmTqU505rLtOQTjlf9Zzsr2Jmza64HuzK Ui8r8dXHGK3oUZ49rhECQQD175WgBvEG/vwfLFFxK1b4pzeWYTjNgEYBvYhjHjxQ Q3fic/msjxO6yqzLsJneu9IyLUKlWWPZ5AoVTwXNUXKPAkEA7o9T2ruKXw215x29 gGQMSuUJrBJ4J2T2zv2F6VPQyuD1xZpVYU6fRTGBPnkw9dYZ0xFdRQ4I2cyKVrD+ nt0qVQJAOmMZ67caK+YHZ0M3Rp3adQgF+26zdJ5agHlF0vpPqWKLKLkN8ni5X2RU p7sSnL2MhpsWMnlJamZoOmzbXMZUYwJBAIEe8rQhbfOk6B//6OHlRQIElgect4wb CbtfXWu9AfXNbTlXH39bnrlE4j9+ORHWoIOtkl4eCoxYOUhS5H34F0ECQAjz4laB Yt1Zx5df0+67go2Ya6THgZnDafne8wqnQW6m5DEyidFZM36QDvpyrxAiPzG4QGR3 HLU0VEwSQa7rvmY= -----END PRIVATE KEY-----
3. PKCS8格式私钥再转换为PKCS1格式
openssl rsa -in pkcs8.pem -out pkcs1.pem
-----BEGIN RSA PRIVATE KEY----- MIICXQIBAAKBgQDlLm5+Kosybacfp8hzjn1fl2wT7Au2lm5SEtz6r+/wwSfq5KfY H8q1AO/C92IwEpplNbrqYmOXQu6P07mg0lQOCvE5sdtmAvD2ex3wCef8lWmgdh5q Uo4OMcmoSz3IAp/7/FnMag1IelSfdronPBDxazp6NUmQZITsYK6CsEl/ewIDAQAB AoGBAJkMdvF+i9Kzc6YqMC0rfQJ3Zs+vFOtsbmQVAMnQ8JWBCJ1O8d/c60wRQgyb lFCyO7VXOmoIJqX/Jr2aER8bFtG+Yxy6jsMu3ynwMwbhcVmCWCmZoWuE5pZdEJk6 lOdOay7TkE45X/Wc7K9iZs2uuB7sylIvK/HVxxit6FGePa4RAkEA9e+VoAbxBv78 HyxRcStW+Kc3lmE4zYBGAb2IYx48UEN34nP5rI8Tusqsy7CZ3rvSMi1CpVlj2eQK FU8FzVFyjwJBAO6PU9q7il8NtecdvYBkDErlCawSeCdk9s79helT0Mrg9cWaVWFO n0UxgT55MPXWGdMRXUUOCNnMilaw/p7dKlUCQDpjGeu3GivmB2dDN0ad2nUIBftu s3SeWoB5RdL6T6liiyi5DfJ4uV9kVKe7Epy9jIabFjJ5SWpmaDps21zGVGMCQQCB HvK0IW3zpOgf/+jh5UUCBJYHnLeMGwm7X11rvQH1zW05Vx9/W565ROI/fjkR1qCD rZJeHgqMWDlIUuR9+BdBAkAI8+JWgWLdWceXX9Puu4KNmGukx4GZw2n53vMKp0Fu puQxMonRWTN+kA76cq8QIj8xuEBkdxy1NFRMEkGu675m -----END RSA PRIVATE KEY-----
可以看出结果和1是一致的；
4. 从pkcs1私钥中生成pkcs8公钥
openssl rsa -in private.pem -pubout -out public.pem
-----BEGIN PUBLIC KEY----- MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDlLm5+Kosybacfp8hzjn1fl2wT 7Au2lm5SEtz6r+/wwSfq5KfYH8q1AO/C92IwEpplNbrqYmOXQu6P07mg0lQOCvE5 sdtmAvD2ex3wCef8lWmgdh5qUo4OMcmoSz3IAp/7/FnMag1IelSfdronPBDxazp6 NUmQZITsYK6CsEl/ewIDAQAB -----END PUBLIC KEY-----
5. 从pkcs8私钥中生成pkcs8公钥
openssl rsa -in pkcs8.pem -pubout -out public_pkcs8.pem
-----BEGIN PUBLIC KEY----- MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDlLm5+Kosybacfp8hzjn1fl2wT 7Au2lm5SEtz6r+/wwSfq5KfYH8q1AO/C92IwEpplNbrqYmOXQu6P07mg0lQOCvE5 sdtmAvD2ex3wCef8lWmgdh5qUo4OMcmoSz3IAp/7/FnMag1IelSfdronPBDxazp6 NUmQZITsYK6CsEl/ewIDAQAB -----END PUBLIC KEY-----
可以看出结果和4是一样的；
6. pkcs8公钥转pkcs1公钥
openssl rsa -pubin -in public.pem -RSAPublicKey_out
-----BEGIN RSA PUBLIC KEY----- MIGJAoGBAOUubn4qizJtpx+nyHOOfV+XbBPsC7aWblIS3Pqv7/DBJ+rkp9gfyrUA 78L3YjASmmU1uupiY5dC7o/TuaDSVA4K8Tmx22YC8PZ7HfAJ5/yVaaB2HmpSjg4x yahLPcgCn/v8WcxqDUh6VJ92uic8EPFrOno1SZBkhOxgroKwSX97AgMBAAE= -----END RSA PUBLIC KEY----- openssl rsa -pubin -in public_pkcs8.pem -RSAPublicKey_out -----BEGIN RSA PUBLIC KEY----- MIGJAoGBAOUubn4qizJtpx+nyHOOfV+XbBPsC7aWblIS3Pqv7/DBJ+rkp9gfyrUA 78L3YjASmmU1uupiY5dC7o/TuaDSVA4K8Tmx22YC8PZ7HfAJ5/yVaaB2HmpSjg4x yahLPcgCn/v8WcxqDUh6VJ92uic8EPFrOno1SZBkhOxgroKwSX97AgMBAAE= -----END RSA PUBLIC KEY-----
可以看出转换的结果是一致的；
7. pkcs1公钥转换为pkcs8公钥
openssl rsa -RSAPublicKey_in -in pub_pkcs1.pem -pubout
-----BEGIN PUBLIC KEY----- MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDlLm5+Kosybacfp8hzjn1fl2wT 7Au2lm5SEtz6r+/wwSfq5KfYH8q1AO/C92IwEpplNbrqYmOXQu6P07mg0lQOCvE5 sdtmAvD2ex3wCef8lWmgdh5qUo4OMcmoSz3IAp/7/FnMag1IelSfdronPBDxazp6 NUmQZITsYK6CsEl/ewIDAQAB -----END PUBLIC KEY-----
可以看到和上面4，5的结果是一致的；
最后一点：
iOS上用的是pkcs8格式的公钥
openssl用的是pkcs1格式的公钥
知道私钥以后是可以导出公钥的，所以私钥一定要保证安全
知道公钥不可以导出私钥
