Help with OpenSSL RSA

[Starfry Starfry]

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.

 

[Aaron Patterson]

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.

How about Base64 ecoding?

[key.public_key.n.to_s].pack('m')

 

[John Lane]

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[rivate_key]
k = RSA.new(128)
session[rivate_key] = k.to_pem
session[ublic_modulus] = k.public_key.n.to_s
session[ublic_exponent] = k.public_key.e.to_s

end
@private_key = session[rivate_key]
@public_modulus = session[ublic_modulus]
@public_exponent = session[ublic_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!

 

[Shandy Nantz]

def generate_keys
unless session[rivate_key]
k = RSA.new(128)
session[rivate_key] = k.to_pem
session[ublic_modulus] = k.public_key.n.to_s
session[ublic_exponent] = k.public_key.e.to_s

end
@private_key = session[rivate_key]
@public_modulus = session[ublic_modulus]
@public_exponent = session[ublic_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

 

[yermej]

def generate_keys
unless session[rivate_key]
k = RSA.new(128)
session[rivate_key] = k.to_pem
session[ublic_modulus] = k.public_key.n.to_s
session[ublic_exponent] = k.public_key.e.to_s

end
@private_key = session[rivate_key]
@public_modulus = session[ublic_modulus]
@public_exponent = session[ublic_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

This seems to work if you want it as a hex string:

key = OpenSSL:Key::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)

 

[Shandy Nantz]

@public_modulus = session[ublic_modulus]

Did this ever get resolved? This is the exact problem that I am trying
to solve. Thanks,

-S

This seems to work if you want it as a hex string:

key = OpenSSL:Key::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

 

[Rick DeNatale]

@public_modulus = session[ublic_modulus]
Did this ever get resolved? This is the exact problem that I am trying
to solve. Thanks,

-S

This seems to work if you want it as a hex string:

key = OpenSSL:Key::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.