# Help with OpenSSL RSA **URL:** \ **Category:** Ruby\ **Created:** [August 8, 2007, 12:05am UTC](https://www.ruby-forum.com/t/help-with-openssl-rsa/111501 "2007-08-08T00:05:24Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![johnlester](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e480ec/32.png) [@johnlester](https://www.ruby-forum.com/u/johnlester)\ **Post date:** [August 8, 2007, 12:05am UTC](https://www.ruby-forum.com/t/help-with-openssl-rsa/111501/1 "2007-08-08T00:05:24Z")
Hi, I’m writing a little code to do some RSA stuff and I need to extract the public exponent and modulus for passing to a browser that will use them in Javascript. I’ve done considerable digging but have drawn a blank as I can’t find any complete documentation of the full RSA class definition. What I am trying right now is to do: key = RSA.new(1024) private\_key = key.to\_pem public\_modulus = key.public\_key.n public\_exponent = key.public\_key.e This generates a new key and assigns the private key to a variable. I’d like to get the public exponent and modulus returned as a hex encoded string, similar to the output of “openssl rsa -noout -modulus” However, I can’t find suitable documentation so I don’t know what method (if any) I can use. I’d hoped for “key.public\_key.n.to\_h” but that does not seem to work. So, If anyone can give advice I’d appreciate it! Also, A general question: how do I look up class definitions of “standard” classes that are not documented in RDoc? Is there something similar to a C header file? (sorry, I’m quite new to Ruby). Many thanks for your help. ---
**Author:** ![johnlester](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e480ec/32.png) [@johnlester](https://www.ruby-forum.com/u/johnlester)\ **Post date:** [August 8, 2007, 1:26am UTC](https://www.ruby-forum.com/t/help-with-openssl-rsa/111501/2 "2007-08-08T01:26:24Z")
On Wed, Aug 08, 2007 at 07:05:22AM +0900, Starfry Starfry wrote: > key = RSA.new(1024) > not seem to work. > How about Base64 ecoding? [key.public\_key.n.to\_s].pack(‘m’) ---
**Author:** ![johnlester](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e480ec/32.png) [@johnlester](https://www.ruby-forum.com/u/johnlester)\ **Post date:** [August 9, 2007, 10:31am UTC](https://www.ruby-forum.com/t/help-with-openssl-rsa/111501/3 "2007-08-09T10:31:16Z")
Aaron P. wrote: > On Wed, Aug 08, 2007 at 07:05:22AM +0900, Starfry Starfry wrote: > > > key = RSA.new(1024) > > not seem to work. > > How about Base64 ecoding? > > [key.public\_key.n.to\_s].pack(‘m’) I could not get pack to work as you described. My code is below. I have taken a different tack, to get my Javaption side to work with the modulus and exponent in decimal. def generate\_keys unless session[:private\_key] k = RSA.new(128) session[:private\_key] = k.to\_pem session[:public\_modulus] = k.public\_key.n.to\_s session[:public\_exponent] = k.public\_key.e.to\_s ``` end @private_key = session[:private_key] @public_modulus = session[:public_modulus] @public_exponent = session[:public_exponent] ``` end I’d still like to be able to get this out of Ruby in Hex If only I could find out the available methods in the RSA class (as I said before the RDoc does not include anything about this class). Thanks! ---
**Author:** ![johnlester](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e480ec/32.png) [@johnlester](https://www.ruby-forum.com/u/johnlester)\ **Post date:** [December 13, 2007, 4:24pm UTC](https://www.ruby-forum.com/t/help-with-openssl-rsa/111501/4 "2007-12-13T16:24:38Z")
John L. wrote: > def generate\_keys > unless session[:private\_key] > k = RSA.new(128) > session[:private\_key] = k.to\_pem > session[:public\_modulus] = k.public\_key.n.to\_s > session[:public\_exponent] = k.public\_key.e.to\_s > > ``` > end > @private_key = session[:private_key] > @public_modulus = session[:public_modulus] > @public_exponent = session[:public_exponent] > > ``` > > end > > I’d still like to be able to get this out of Ruby in Hex > > If only I could find out the available methods in the RSA class (as I > said before the RDoc does not include anything about this class). > > Thanks! Did this ever get resolved? This is the exact problem that I am trying to solve. Thanks, -S ---
**Author:** ![johnlester](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e480ec/32.png) [@johnlester](https://www.ruby-forum.com/u/johnlester)\ **Post date:** [December 13, 2007, 5:52pm UTC](https://www.ruby-forum.com/t/help-with-openssl-rsa/111501/5 "2007-12-13T17:52:41Z")
yermej wrote: > On Dec 13, 9:24 am, Shandy N. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > > > ``` > > > @public_modulus = session[:public_modulus] > > > > > > ``` > > > > Did this ever get resolved? This is the exact problem that I am trying > > to solve. Thanks, > > > > ## -S > > > > Posted viahttp://www.ruby-forum.com/. > > This seems to work if you want it as a hex string: > > key = OpenSSL::PKey::RSA.new(1024) > private\_key = key.to\_pem > public\_modulus = key.public\_key.n.to\_s(16) > public\_exponent = key.public\_key.e.to\_s(16) This does work thank you. Does anyone know how to get at all the parts that make up a public key such as the inverse? Thanks ---
**Author:** ![johnlester](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e480ec/32.png) [@johnlester](https://www.ruby-forum.com/u/johnlester)\ **Post date:** [December 13, 2007, 4:50pm UTC](https://www.ruby-forum.com/t/help-with-openssl-rsa/111501/6 "2007-12-13T16:50:53Z")
On Dec 13, 9:24 am, Shandy N. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > ``` > > @public_modulus = session[:public_modulus] > > > > ``` > > Did this ever get resolved? This is the exact problem that I am trying > to solve. Thanks, > > ## -S > > Posted viahttp://www.ruby-forum.com/. This seems to work if you want it as a hex string: key = OpenSSL::PKey::RSA.new(1024) private\_key = key.to\_pem public\_modulus = key.public\_key.n.to\_s(16) public\_exponent = key.public\_key.e.to\_s(16) ---
**Author:** ![johnlester](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e480ec/32.png) [@johnlester](https://www.ruby-forum.com/u/johnlester)\ **Post date:** [December 13, 2007, 9:06pm UTC](https://www.ruby-forum.com/t/help-with-openssl-rsa/111501/7 "2007-12-13T21:06:03Z")
On 12/13/07, Shandy N. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > This seems to work if you want it as a hex string: > > > > key = OpenSSL::PKey::RSA.new(1024) > > private\_key = key.to\_pem > > public\_modulus = key.public\_key.n.to\_s(16) > > public\_exponent = key.public\_key.e.to\_s(16) > > This does work thank you. Does anyone know how to get at all the parts > that make up a public key such as the inverse? Thanks I’m pretty sure that you can’t extract the inverse from a public key. The whole point of a public/private key pair is that it’s extremely difficult to compute the private key from the public key. – Rick DeNatale My blog on Ruby [http://talklikeaduck.denhaven2.com/](http://talklikeaduck.denhaven2.com/)