openssl RSA keys

Create RSA key pair

openssl genrsa -out keys.pem 2048

To get public key (modulus)

openssl rsa -text -in keys.pem

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HOWTO keys

http://www.openssl.org/docs/HOWTO/keys.txt

Keys are the basis of public key algorithms and PKI.  Keys usually
come in pairs, with one half being the public key and the other half
being the private key.  With OpenSSL, the private key contains the
public key information as well, so a public key doesn't need to be
generated separately.

 

[wiki] RSA (algorithm)
http://en.wikipedia.org/wiki/RSA_%28algorithm%29

[wiki] RSA加密演算法 - 维基百科，自由的百科全书
http://zh.wikipedia.org/wiki/RSA%E5%8A%A0%E5%AF%86%E6%BC%94%E7%AE%97%E6%B3%95