OpenSSL "genrsa 32" - Generate RSA Short Keys

Q

How to generate a new RSA key pair with a shorter key size using OpenSSL "genrsa" command?

✍: FYIcenter.com

A

If you need a new RSA key pair with a shorter key size for testing purpose, you can use the OpenSSL "genrsa" command as shown below:

C:\Users\fyicenter>\local\openssl\openssl.exe

OpenSSL> genrsa -out my_rsa_short.key 32
Generating RSA private key, 32 bit long modulus
.+++++++++++++++++++++++++++
.+++++++++++++++++++++++++++
e is 65537 (0x10001)

OpenSSL> rsa -in my_rsa_short.key -text
Private-Key: (32 bit)
modulus: 2860622833 (0xaa81a3f1)
publicExponent: 65537 (0x10001)
privateExponent: 2570348229 (0x993466c5)
prime1: 56039 (0xdae7)
prime2: 51047 (0xc767)
exponent1: 53283 (0xd023)
exponent2: 28991 (0x713f)
coefficient: 23967 (0x5d9f)

writing RSA key
-----BEGIN RSA PRIVATE KEY-----
MC0CAQACBQCqgaPxAgMBAAECBQCZNGbFAgMA2ucCAwDHZwIDANAjAgJxPwICXZ8=
-----END RSA PRIVATE KEY-----

What this test tells us:

  • OpenSSL allows you to generate shorter RSA keys. The shortest ones are 32 bits. But don't use them in production systems. Any keys less than 2048-bit long is considered as unsafe.

 

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2020-10-17, 1505👍, 2💬