# RSA Java/Ruby **URL:** \ **Category:** Ruby\ **Created:** [September 4, 2006, 3:35pm UTC](https://www.ruby-forum.com/t/rsa-java-ruby/67487 "2006-09-04T15:35:23Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![jverger](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/49beb7/32.png) [@jverger](https://www.ruby-forum.com/u/jverger)\ **Post date:** [September 4, 2006, 3:35pm UTC](https://www.ruby-forum.com/t/rsa-java-ruby/67487/1 "2006-09-04T15:35:23Z")
Hi all, I’ve been reading in this list about crypting with RSA but I don’t get it to work. I beg your help. I believe one of the problems I’m having is that the different values (.e , .n , .d ) are being given in decimal format, while the java function will need hexaedcimal format. Please, any hint or idea on how to encrypt/verify based on RSA with Ruby? any other library? Or … how can I create an RSA private key based on hexadecimal values of n, e and d? How can I convert decimal values to hex? thanks a lot, Jean Some code: In the client javascript to encrypt the password (based on [RSA In JavaScript - ohdave.com](http://www.ohdave.com/rsa)) In the server, the following code: # key.pem is generated with “openssl genrsa -out key512.pem 512” in the # command line private\_key = PKey::RSA.new(File.open(“key.pem”).read, nil) # Crypting with the public, decrypting with the private @pwdOriginal = “uno\_dos\_tres” @pwdCrypted\_PubPriv = private\_key.public\_encrypt(@pwdOriginal) @pwdDecrypted\_PubPriv = private\_key.private\_decrypt(@pwdCrypted\_PubPriv) # This values are generated out the .pem file @f\_e = private\_key.e @f\_d = private\_key.d.to\_s @f\_n = private\_key.n @f\_public = private\_key.public\_key @f\_private = private\_key.to\_s ---
**Author:** ![jverger](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/49beb7/32.png) [@jverger](https://www.ruby-forum.com/u/jverger)\ **Post date:** [September 5, 2006, 7:09am UTC](https://www.ruby-forum.com/t/rsa-java-ruby/67487/2 "2006-09-05T07:09:11Z")
On 9/4/06, Jean V. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > based on hexadecimal values of n, e and d? How can I convert decimal > > @f\_e = private\_key.e > @f\_d = private\_key.d.to\_s > @f\_n = private\_key.n > @f\_public = private\_key.public\_key > @f\_private = private\_key.to\_s Hi, 1. your code seems to work fine (if you fix the file name, add require ‘openssl’ and include OpenSSL, alternatively prefix Pkey with OpenSSL:🙂 2. dec-\> hex: “%x” % 123 #=\> “7b” “%X” % 123 #=\> “7B” 3. Just a note: Java and Javascript are two different languages 4. Are you sure you want to send the private key over the wire? 5. The private key has another components besides e,d,n that speed up the decryption/signature generation significantly. ---
**Author:** ![jverger](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/49beb7/32.png) [@jverger](https://www.ruby-forum.com/u/jverger)\ **Post date:** [September 5, 2006, 11:17am UTC](https://www.ruby-forum.com/t/rsa-java-ruby/67487/3 "2006-09-05T11:17:48Z")
Hi, thanks for your advices, 1. Is there any way to generate the RSA Key with e, d and n? (instead of using the pem file? 2. The output that I’m geetting is out of the “regular” character range … Im getting some weird characters. I guess it is normal when crypting, but with the javascript RSA model I don’t get any “weird character”. Anyway to limit the output? This is the output in a browser: [http://i108.photobucket.com/albums/n27/jverger/rsaRuby.png](http://i108.photobucket.com/albums/n27/jverger/rsaRuby.png) 3. Finally … when using this code i get a different encrypted string every time I run the code! 🙂 How can that be? I mean, given the same .pem file, i get a different encryption, although then, the verification is fine. private\_key = PKey::RSA.new(File.open(“key.pem”).read, nil) @pwdOriginal = “uno\_dos\_tres” @pwdCrypted\_PubPriv = private\_key.public\_encrypt(@pwdOriginal) @pwdDecrypted\_PubPriv = private\_key.private\_decrypt(@pwdCrypted\_PubPriv) thanks again for your help, Jean ---
**Author:** ![jverger](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/49beb7/32.png) [@jverger](https://www.ruby-forum.com/u/jverger)\ **Post date:** [September 5, 2006, 11:57am UTC](https://www.ruby-forum.com/t/rsa-java-ruby/67487/4 "2006-09-05T11:57:55Z")
On 9/5/06, Jean V. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Hi, > thanks for your advices, > > 1. Is there any way to generate the RSA Key with e, d and n? (instead > of using the pem file? try PKey::RSA.generate(512) > 1. The output that I’m geetting is out of the “regular” character > range … Im getting some weird characters. I guess it is normal when > crypting, but with the javascript RSA model I don’t get any “weird > character”. Anyway to limit the output? This is the output in a > browser: > [http://i108.photobucket.com/albums/n27/jverger/rsaRuby.png](http://i108.photobucket.com/albums/n27/jverger/rsaRuby.png) You’re getting bytes, javascript gives you hex-encoded data > 1. Finally … when using this code i get a different encrypted string > every time I run the code! 🙂 How can that be? I mean, given the same > .pem file, i get a different encryption, although then, the > verification is fine. PKCS#1 add random padding to the encrypted data to avoid situation, when the same data is always encrypted as same ciphertext. I’d encourage you to read some literature on the topic, as I wrote some time ago ([Asymmetric encryption options - Ruby - Ruby-Forum](http://www.ruby-forum.com/topic/79044)), encryption is easy to get messed up, and your efforts would be ruined. See the thread for some links. You need to understand the basics if you want your encryption fulfill its purpose. At least read PKCS#1 standard. You’ll learn about the padding schemes and various attacks on it there. Please don’t get me wrong, this is meant as an advice to not get burned. I’ll be glad if I’m wrong in this case 😉 ---
**Author:** ![jverger](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/49beb7/32.png) [@jverger](https://www.ruby-forum.com/u/jverger)\ **Post date:** [September 5, 2006, 1:34pm UTC](https://www.ruby-forum.com/t/rsa-java-ruby/67487/5 "2006-09-05T13:34:06Z")
On 9/5/06, Jean V. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > 1. If I use this: PKey::RSA.generate(512) I believe that I still have > a random key generated (instead of one with n, d and e desired). From > not much difference than using this: > #openssl genrsa -out key.pem 256 > PKey::RSA.new(File.open(“/key.pem”).read, nil) Sorry, I misunderstood. This is how it _could_ be done. I’ve just read the sources, haven’t tried. key = PKey.RSA.new key.n, key.e, key.d = n,e,d If you know a bit of C, read the sources of ruby, everything is there 😉 namely: src/ext/openssl/ossl\_pkey\_rsa.c ---
**Author:** ![jverger](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/49beb7/32.png) [@jverger](https://www.ruby-forum.com/u/jverger)\ **Post date:** [September 5, 2006, 1:10pm UTC](https://www.ruby-forum.com/t/rsa-java-ruby/67487/6 "2006-09-05T13:10:03Z")
Hi, no problem … I truly understand what you mean by reading more. 1. Definitely your hint on PKCS#1 … is saved me some headaches that I couldn’t understand why. 2. If I use this: PKey::RSA.generate(512) I believe that I still have a random key generated (instead of one with n, d and e desired). From not much difference than using this: #openssl genrsa -out key.pem 256 PKey::RSA.new(File.open("/key.pem").read, nil) 3. Finally, thanks for this pearl of wisdow … so I understand that the crypted password in the client side (javascript) has to be converted to bytes in order to be verified. thanks for your help, Jean