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jdw
Asked: 2011-10-28 11:37:21 +0800 CST

I have a keypair. How do I determine the key length?

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Using OpenSSL from the command line in Linux, is there some way to examine a key (either public or private) to determine the key size?

linux encryption openssl

2 Answers

  1. Best Answer
    openssl rsa -in private.key -text -noout

    The top line of the output will display the key size.

    For example:

    Private-Key: (2048 bit)

    To view the key size from a certificate:

    $ openssl x509 -in public.pem -text -noout | grep "RSA Public Key"
RSA Public Key: (2048 bit)
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  2. The first (2048) is the bit length of the key:

     $ ssh-keygen -lf /etc/ssh/rsa_key.pub 
 2048 91:1c:ae:17:16:...
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