Ok, time to ask the question here.. I have been battling over this one for
sometime now and just have to ask it.
I have created a few classes that I use to act a security keys. These
classes get serialized using a binary formatter and then symmetrically
encrypted. The app will deserialize them and use the contents to judge
licensing capabilities, etc.
Currently the license key and vectors are stored in the code. I don't like
the idea simply because it allows someone with a decompile to get at them.
Yes, I can obfuscate the code but being paranoid like I am I have a feeling
that is just not enough.
My real biggest fear besides the fact that someone can use the key to
decrypt the data is that someone can also use the same key to create a
program that will generate fake license keys for my app.
In another case I have to send a class across a wire on a remoting channel
and the class is going to have a users name and password in it. Again, being
the paranoid programmer that I am I am really afraid of someone with a
sniffer out there looking at the raw bits. I would like to encrypt the
password before I send the class across the wire. Again, I know that I can
just hard code the keys into the app but we all know what I feel about that.
I know that I could use asymmetrical encryption and that gives me the
ability to release a public key that can only be used to decrypt and that
takes care of part of it but from what I have seen asymmetrical encryption
is a royal pain in the butt because it only encrypts data of a maximum size
so I would have to take that into account when I am serializing data and
possibly split the data up into checks, each one encrypted.. Not a clean
option really.
I know already, I have read tones of thing on remoting and how to build
encryption sinks to be used for cases like this, but I really don't need to
encrypt the entire message, just one part of it.
There HAS to be a way to reliably use symmetrical encryption without hard
coding the keys into the code but also protecting them from being used by
other people.
Any simple ideas to this tough question?
14  1949 
Protecting a shared session key is always a problem. If it was not for
this, things would be a lot easier and a lot less books would be written on
it. However, you may not need symmetric key depending on exactly what your
sending and what goes which way (i.e. what to server and what to client.)
If using asymmetric keys, you need at least the server's public key to get
started. This could also be the server cert, but not required. Your assem
can have the public key already in it if you sign the assembly. So the
server will know the private key and the client's will know the server's
public key. Now encrypt your fields with the servers public key. Only the
server (the owner of the private key) can decrypt the fields. Your server
gens a reply (say an xml document with fields.) The server will sign the
reply with private key. Your client can verify server msg is good as it can
validate the signature using the server's public key it has. Now you have a
valid license. However, unless you add more logic, it is valid for *any
machine. You then need to come up with some method to identify a user's
particular machine (i.e. machine hash including user name, mac, domain name,
etc) and the server's reply will include this hash as you also send it in
the request. So your client will verify lic and fail if signature does not
validate. It will then verify the machine hash matches what you dynamically
calculate and compare the two to proceed or fail. No shared secret using
this method - only the server's public key retrieved from the assembly. If
you need to encrypt stuff sent to the client, then more work is needed.
There are a few options, but the best is to not require anything in the
reply that requires encryption. You can verify the lic was produced by the
server via just the signature and the lic will not work for everyone because
of the machine hash. HTH.
--
William Stacey, MVP http://mvp.support.microsoft.com
"Ray Cassick (Home)" <rc************ @enterprocity.c om> wrote in message
news:##******** ******@TK2MSFTN GP09.phx.gbl... Ok, time to ask the question here.. I have been battling over this one for
sometime now and just have to ask it.
I have created a few classes that I use to act a security keys. These
classes get serialized using a binary formatter and then symmetrically
encrypted. The app will deserialize them and use the contents to judge
licensing capabilities, etc.
Currently the license key and vectors are stored in the code. I don't like
the idea simply because it allows someone with a decompile to get at them.
Yes, I can obfuscate the code but being paranoid like I am I have a
feeling that is just not enough.
My real biggest fear besides the fact that someone can use the key to
decrypt the data is that someone can also use the same key to create a
program that will generate fake license keys for my app.
In another case I have to send a class across a wire on a remoting channel
and the class is going to have a users name and password in it. Again,
being the paranoid programmer that I am I am really afraid of someone with a
sniffer out there looking at the raw bits. I would like to encrypt the
password before I send the class across the wire. Again, I know that I can
just hard code the keys into the app but we all know what I feel about
that.
I know that I could use asymmetrical encryption and that gives me the
ability to release a public key that can only be used to decrypt and that
takes care of part of it but from what I have seen asymmetrical encryption
is a royal pain in the butt because it only encrypts data of a maximum
size so I would have to take that into account when I am serializing data and
possibly split the data up into checks, each one encrypted.. Not a clean
option really.
I know already, I have read tones of thing on remoting and how to build
encryption sinks to be used for cases like this, but I really don't need
to encrypt the entire message, just one part of it.
There HAS to be a way to reliably use symmetrical encryption without hard
coding the keys into the code but also protecting them from being used by
other people.
Any simple ideas to this tough question?
SSL uses asymmetric encryption, but only for the handshake. It's a good
pattern to follow.
Embed the public key of your server in your code. Make it available all you
want.
When a client wants to contact you, he asks first for the cert. give it to
him. Validate the cert. It should be signed by a trusted authority.
Next, the client creates a random number. This is the symmetrical key. The
client encrypts the random number using the public key of the server, and
passes it upstream to the server. It also hashes the UNENCRYPTED form of
the key and keeps it around in memory. The server gets the cyphertext,
unencrypts it, and passes back an acknowledgement , in cleartext, containing
the Hash of the unencrypted key. The client receives the hash and compares
it to the hash that he is holding. If it matches, both sides now have a
symmetrical key that they can use.
Now, encrypt using the symmetrical key. It is much faster and easier to
use.
--
--- Nick Malik [Microsoft]
MCSD, CFPS, Certified Scrummaster http://blogs.msdn.com/nickmalik
Disclaimer: Opinions expressed in this forum are my own, and not
representative of my employer.
I do not answer questions on behalf of my employer. I'm just a
programmer helping programmers.
--
"Ray Cassick (Home)" <rc************ @enterprocity.c om> wrote in message
news:%2******** **********@TK2M SFTNGP09.phx.gb l... Ok, time to ask the question here.. I have been battling over this one for
sometime now and just have to ask it.
I have created a few classes that I use to act a security keys. These
classes get serialized using a binary formatter and then symmetrically
encrypted. The app will deserialize them and use the contents to judge
licensing capabilities, etc.
Currently the license key and vectors are stored in the code. I don't like
the idea simply because it allows someone with a decompile to get at them.
Yes, I can obfuscate the code but being paranoid like I am I have a
feeling that is just not enough.
My real biggest fear besides the fact that someone can use the key to
decrypt the data is that someone can also use the same key to create a
program that will generate fake license keys for my app.
In another case I have to send a class across a wire on a remoting channel
and the class is going to have a users name and password in it. Again,
being the paranoid programmer that I am I am really afraid of someone with a
sniffer out there looking at the raw bits. I would like to encrypt the
password before I send the class across the wire. Again, I know that I can
just hard code the keys into the app but we all know what I feel about
that.
I know that I could use asymmetrical encryption and that gives me the
ability to release a public key that can only be used to decrypt and that
takes care of part of it but from what I have seen asymmetrical encryption
is a royal pain in the butt because it only encrypts data of a maximum
size so I would have to take that into account when I am serializing data and
possibly split the data up into checks, each one encrypted.. Not a clean
option really.
I know already, I have read tones of thing on remoting and how to build
encryption sinks to be used for cases like this, but I really don't need
to encrypt the entire message, just one part of it.
There HAS to be a way to reliably use symmetrical encryption without hard
coding the keys into the code but also protecting them from being used by
other people.
Any simple ideas to this tough question?
Thanks... This defiantly sounds like something I can put into the system...
"Nick Malik [Microsoft]" <ni*******@hotm ail.nospam.com> wrote in message
news:Zt******** ************@co mcast.com... SSL uses asymmetric encryption, but only for the handshake. It's a good
pattern to follow.
Embed the public key of your server in your code. Make it available all
you want.
When a client wants to contact you, he asks first for the cert. give it
to him. Validate the cert. It should be signed by a trusted authority.
Next, the client creates a random number. This is the symmetrical key.
The client encrypts the random number using the public key of the server, and
passes it upstream to the server. It also hashes the UNENCRYPTED form of
the key and keeps it around in memory. The server gets the cyphertext,
unencrypts it, and passes back an acknowledgement , in cleartext,
containing the Hash of the unencrypted key. The client receives the hash and
compares it to the hash that he is holding. If it matches, both sides now have a
symmetrical key that they can use.
Now, encrypt using the symmetrical key. It is much faster and easier to
use.
--
--- Nick Malik [Microsoft]
MCSD, CFPS, Certified Scrummaster
http://blogs.msdn.com/nickmalik
Disclaimer: Opinions expressed in this forum are my own, and not
representative of my employer.
I do not answer questions on behalf of my employer. I'm just a
programmer helping programmers.
--
"Ray Cassick (Home)" <rc************ @enterprocity.c om> wrote in message
news:%2******** **********@TK2M SFTNGP09.phx.gb l... Ok, time to ask the question here.. I have been battling over this one
for sometime now and just have to ask it.
I have created a few classes that I use to act a security keys. These
classes get serialized using a binary formatter and then symmetrically
encrypted. The app will deserialize them and use the contents to judge
licensing capabilities, etc.
Currently the license key and vectors are stored in the code. I don't
like the idea simply because it allows someone with a decompile to get at
them. Yes, I can obfuscate the code but being paranoid like I am I have a
feeling that is just not enough.
My real biggest fear besides the fact that someone can use the key to
decrypt the data is that someone can also use the same key to create a
program that will generate fake license keys for my app.
In another case I have to send a class across a wire on a remoting
channel and the class is going to have a users name and password in it. Again,
being the paranoid programmer that I am I am really afraid of someone with a
sniffer out there looking at the raw bits. I would like to encrypt the
password before I send the class across the wire. Again, I know that I
can just hard code the keys into the app but we all know what I feel about
that.
I know that I could use asymmetrical encryption and that gives me the
ability to release a public key that can only be used to decrypt and
that takes care of part of it but from what I have seen asymmetrical
encryption is a royal pain in the butt because it only encrypts data of a maximum
size so I would have to take that into account when I am serializing data and
possibly split the data up into checks, each one encrypted.. Not a clean
option really.
I know already, I have read tones of thing on remoting and how to build
encryption sinks to be used for cases like this, but I really don't need
to encrypt the entire message, just one part of it.
There HAS to be a way to reliably use symmetrical encryption without
hard coding the keys into the code but also protecting them from being used
by other people.
Any simple ideas to this tough question?
Thanks Nick. Just thinking... If the key is hashed by the server using a
simple hash like SHA1(key) or something, then it is pretty easy to brute
force the same key by hashing all keys and hashing them. Naturally,
starting from 0 may take some time, but a 16 byte key in a simple hash with
no other encryption could be found pretty easy - no? I might rather hash
the key along with the other data elements and sign it with the private key.
Thoughts?
BTW - any relation to Eddy Malik of MS?
--
William Stacey, MVP http://mvp.support.microsoft.com
"Nick Malik [Microsoft]" <ni*******@hotm ail.nospam.com> wrote in message
news:Zt******** ************@co mcast.com... SSL uses asymmetric encryption, but only for the handshake. It's a good
pattern to follow.
Embed the public key of your server in your code. Make it available all
you want.
When a client wants to contact you, he asks first for the cert. give it
to him. Validate the cert. It should be signed by a trusted authority.
Next, the client creates a random number. This is the symmetrical key.
The client encrypts the random number using the public key of the server, and
passes it upstream to the server. It also hashes the UNENCRYPTED form of
the key and keeps it around in memory. The server gets the cyphertext,
unencrypts it, and passes back an acknowledgement , in cleartext,
containing the Hash of the unencrypted key. The client receives the hash and
compares it to the hash that he is holding. If it matches, both sides now have a
symmetrical key that they can use.
Now, encrypt using the symmetrical key. It is much faster and easier to
use.
--
--- Nick Malik [Microsoft]
MCSD, CFPS, Certified Scrummaster
http://blogs.msdn.com/nickmalik
Disclaimer: Opinions expressed in this forum are my own, and not
representative of my employer.
I do not answer questions on behalf of my employer. I'm just a
programmer helping programmers.
--
"Ray Cassick (Home)" <rc************ @enterprocity.c om> wrote in message
news:%2******** **********@TK2M SFTNGP09.phx.gb l... Ok, time to ask the question here.. I have been battling over this one
for sometime now and just have to ask it.
I have created a few classes that I use to act a security keys. These
classes get serialized using a binary formatter and then symmetrically
encrypted. The app will deserialize them and use the contents to judge
licensing capabilities, etc.
Currently the license key and vectors are stored in the code. I don't
like the idea simply because it allows someone with a decompile to get at
them. Yes, I can obfuscate the code but being paranoid like I am I have a
feeling that is just not enough.
My real biggest fear besides the fact that someone can use the key to
decrypt the data is that someone can also use the same key to create a
program that will generate fake license keys for my app.
In another case I have to send a class across a wire on a remoting
channel and the class is going to have a users name and password in it. Again,
being the paranoid programmer that I am I am really afraid of someone with a
sniffer out there looking at the raw bits. I would like to encrypt the
password before I send the class across the wire. Again, I know that I
can just hard code the keys into the app but we all know what I feel about
that.
I know that I could use asymmetrical encryption and that gives me the
ability to release a public key that can only be used to decrypt and
that takes care of part of it but from what I have seen asymmetrical
encryption is a royal pain in the butt because it only encrypts data of a maximum
size so I would have to take that into account when I am serializing data and
possibly split the data up into checks, each one encrypted.. Not a clean
option really.
I know already, I have read tones of thing on remoting and how to build
encryption sinks to be used for cases like this, but I really don't need
to encrypt the entire message, just one part of it.
There HAS to be a way to reliably use symmetrical encryption without
hard coding the keys into the code but also protecting them from being used
by other people.
Any simple ideas to this tough question?
"Ray Cassick (Home)" <rc************ @enterprocity.c om> wrote in message
news:%2******** **********@TK2M SFTNGP09.phx.gb l... Ok, time to ask the question here.. I have been battling over this one for
sometime now and just have to ask it.
I have created a few classes that I use to act a security keys. These
classes get serialized using a binary formatter and then symmetrically
encrypted. The app will deserialize them and use the contents to judge
licensing capabilities, etc.
Currently the license key and vectors are stored in the code. I don't like
the idea simply because it allows someone with a decompile to get at them.
Yes, I can obfuscate the code but being paranoid like I am I have a
feeling
that is just not enough.
This should be more than enough for your average user. Admittedly it won't
stop anyone familiar with .NET, but in that case they just round-trip your
assemblies and remove all licensing code completely, no matter what system
you use.
My real biggest fear besides the fact that someone can use the key to
decrypt the data is that someone can also use the same key to create a
program that will generate fake license keys for my app.
Hmm, I've been writing a simple licensing system:
http://home.imaginet.co.za/codingsanity/Licensing.htm, but I don't
particularly care if the users can read my license file. I use digitally
signed XML files (look at http://www.codeproject.com/dotnet/xmldsiglic.asp),
with the public key embedded in an assembly attribute. Since it's an
asymmetric key, all anyone can do with it it read the files (which they can
do anyway since the files are cleartext). They can't generate a valid new
license file from that information. Round-tripping could easily get around
this system, but frankly it can easily get around any system.
I think it was Jon Skeet who pointed out that if people like your
application enough to be cracking it, you're probably making a bit of cash
from it, so why are you worrying about a tiny percentage cheating?
In another case I have to send a class across a wire on a remoting channel
and the class is going to have a users name and password in it. Again,
being
the paranoid programmer that I am I am really afraid of someone with a
sniffer out there looking at the raw bits. I would like to encrypt the
password before I send the class across the wire. Again, I know that I can
just hard code the keys into the app but we all know what I feel about
that.
I know that I could use asymmetrical encryption and that gives me the
ability to release a public key that can only be used to decrypt and that
takes care of part of it but from what I have seen asymmetrical encryption
is a royal pain in the butt because it only encrypts data of a maximum
size
so I would have to take that into account when I am serializing data and
possibly split the data up into checks, each one encrypted.. Not a clean
option really.
I know already, I have read tones of thing on remoting and how to build
encryption sinks to be used for cases like this, but I really don't need
to
encrypt the entire message, just one part of it.
There HAS to be a way to reliably use symmetrical encryption without hard
coding the keys into the code but also protecting them from being used by
other people.
Any simple ideas to this tough question?
Hey Sean. Just curious. How are you protecting the license so that it is
unique the user and can not be emailed to another user? Using a machine
hash or something and signing that with the rest of the license? What do
you include in your machine hash? do anyway since the files are cleartext). They can't generate a valid new
license file from that information. Round-tripping could easily get around
this system, but frankly it can easily get around any system.
Currently, you can't round-trip a XenoCode'd assembly. This may change in
the future with a new version of ildasm, but can't today. TIA
--
William Stacey, MVP http://mvp.support.microsoft.com
Hi William,
no relation to Eddie Malik.
True, salting the key on both ends will help, but the value that you salt it
with has to be easily calculated by both ends independently of one another.
This helps, but not a whole heckuva lot.
Signing with the private key doesn't provide security, it provides
non-repudiation. In other words, since the public key is public, anyone can
decrypt something encrypted with a public key. However, only the owner of
the private key could have signed it (hence the name).
The way that SSL does it is to add one more step: the private key is used to
encrypt a known phrase (I believe it is the server name from the public key
cert plus the time stamp on the server), signed. The client decrypts with
the private key and then verifies the signature. That way, the client knows
that the server knows the key and knows that only the server could have
signed the response.
--
--- Nick Malik [Microsoft]
MCSD, CFPS, Certified Scrummaster http://blogs.msdn.com/nickmalik
Disclaimer: Opinions expressed in this forum are my own, and not
representative of my employer.
I do not answer questions on behalf of my employer. I'm just a
programmer helping programmers.
--
"William Stacey [MVP]" <st***********@ mvps.org> wrote in message
news:%2******** ********@TK2MSF TNGP12.phx.gbl. .. Thanks Nick. Just thinking... If the key is hashed by the server using a
simple hash like SHA1(key) or something, then it is pretty easy to brute
force the same key by hashing all keys and hashing them. Naturally,
starting from 0 may take some time, but a 16 byte key in a simple hash
with no other encryption could be found pretty easy - no? I might rather hash
the key along with the other data elements and sign it with the private
key. Thoughts?
BTW - any relation to Eddy Malik of MS?
--
William Stacey, MVP
http://mvp.support.microsoft.com
"Nick Malik [Microsoft]" <ni*******@hotm ail.nospam.com> wrote in message
news:Zt******** ************@co mcast.com... SSL uses asymmetric encryption, but only for the handshake. It's a good
pattern to follow.
Embed the public key of your server in your code. Make it available all
you want.
When a client wants to contact you, he asks first for the cert. give it
to him. Validate the cert. It should be signed by a trusted authority.
Next, the client creates a random number. This is the symmetrical key.
The client encrypts the random number using the public key of the server,
and passes it upstream to the server. It also hashes the UNENCRYPTED form
of the key and keeps it around in memory. The server gets the cyphertext,
unencrypts it, and passes back an acknowledgement , in cleartext,
containing the Hash of the unencrypted key. The client receives the hash and
compares it to the hash that he is holding. If it matches, both sides now have
a symmetrical key that they can use.
Now, encrypt using the symmetrical key. It is much faster and easier to
use.
--
--- Nick Malik [Microsoft]
MCSD, CFPS, Certified Scrummaster
http://blogs.msdn.com/nickmalik
Disclaimer: Opinions expressed in this forum are my own, and not
representative of my employer.
I do not answer questions on behalf of my employer. I'm just a
programmer helping programmers.
--
"Ray Cassick (Home)" <rc************ @enterprocity.c om> wrote in message
news:%2******** **********@TK2M SFTNGP09.phx.gb l... Ok, time to ask the question here.. I have been battling over this one for sometime now and just have to ask it.
I have created a few classes that I use to act a security keys. These
classes get serialized using a binary formatter and then symmetrically
encrypted. The app will deserialize them and use the contents to judge
licensing capabilities, etc.
Currently the license key and vectors are stored in the code. I don't like the idea simply because it allows someone with a decompile to get at them. Yes, I can obfuscate the code but being paranoid like I am I have a
feeling that is just not enough.
My real biggest fear besides the fact that someone can use the key to
decrypt the data is that someone can also use the same key to create a
program that will generate fake license keys for my app.
In another case I have to send a class across a wire on a remoting channel and the class is going to have a users name and password in it. Again,
being the paranoid programmer that I am I am really afraid of someone with a
sniffer out there looking at the raw bits. I would like to encrypt the
password before I send the class across the wire. Again, I know that I can just hard code the keys into the app but we all know what I feel about
that.
I know that I could use asymmetrical encryption and that gives me the
ability to release a public key that can only be used to decrypt and that takes care of part of it but from what I have seen asymmetrical encryption is a royal pain in the butt because it only encrypts data of a maximum
size so I would have to take that into account when I am serializing data
and possibly split the data up into checks, each one encrypted.. Not a
clean option really.
I know already, I have read tones of thing on remoting and how to
build encryption sinks to be used for cases like this, but I really don't
need to encrypt the entire message, just one part of it.
There HAS to be a way to reliably use symmetrical encryption without
hard coding the keys into the code but also protecting them from being used by other people.
Any simple ideas to this tough question?
Correction: I meant to say that the symmetric key is used to encrypt the
known phrase, not the private key. My apologies.
--
--- Nick Malik [Microsoft]
MCSD, CFPS, Certified Scrummaster http://blogs.msdn.com/nickmalik
Disclaimer: Opinions expressed in this forum are my own, and not
representative of my employer.
I do not answer questions on behalf of my employer. I'm just a
programmer helping programmers.
--
"Nick Malik [Microsoft]" <ni*******@hotm ail.nospam.com> wrote in message
news:Lu******** ************@co mcast.com... Hi William,
no relation to Eddie Malik.
True, salting the key on both ends will help, but the value that you salt
it with has to be easily calculated by both ends independently of one
another. This helps, but not a whole heckuva lot.
Signing with the private key doesn't provide security, it provides
non-repudiation. In other words, since the public key is public, anyone
can decrypt something encrypted with a public key. However, only the owner of
the private key could have signed it (hence the name).
The way that SSL does it is to add one more step: the private key is used
to encrypt a known phrase (I believe it is the server name from the public
key cert plus the time stamp on the server), signed. The client decrypts with
the private key and then verifies the signature. That way, the client
knows that the server knows the key and knows that only the server could have
signed the response.
--
--- Nick Malik [Microsoft]
MCSD, CFPS, Certified Scrummaster
http://blogs.msdn.com/nickmalik
Disclaimer: Opinions expressed in this forum are my own, and not
representative of my employer.
I do not answer questions on behalf of my employer. I'm just a
programmer helping programmers.
--
"William Stacey [MVP]" <st***********@ mvps.org> wrote in message
news:%2******** ********@TK2MSF TNGP12.phx.gbl. .. Thanks Nick. Just thinking... If the key is hashed by the server using
a simple hash like SHA1(key) or something, then it is pretty easy to brute
force the same key by hashing all keys and hashing them. Naturally,
starting from 0 may take some time, but a 16 byte key in a simple hash with no other encryption could be found pretty easy - no? I might rather
hash the key along with the other data elements and sign it with the private
key. Thoughts?
BTW - any relation to Eddy Malik of MS?
--
William Stacey, MVP
http://mvp.support.microsoft.com
"Nick Malik [Microsoft]" <ni*******@hotm ail.nospam.com> wrote in message
news:Zt******** ************@co mcast.com... SSL uses asymmetric encryption, but only for the handshake. It's a
good pattern to follow.
Embed the public key of your server in your code. Make it available
all you want.
When a client wants to contact you, he asks first for the cert. give
it to him. Validate the cert. It should be signed by a trusted authority.
Next, the client creates a random number. This is the symmetrical
key. The client encrypts the random number using the public key of the server, and passes it upstream to the server. It also hashes the UNENCRYPTED form of the key and keeps it around in memory. The server gets the
cyphertext, unencrypts it, and passes back an acknowledgement , in cleartext,
containing the Hash of the unencrypted key. The client receives the hash and
compares it to the hash that he is holding. If it matches, both sides now
have a symmetrical key that they can use.
Now, encrypt using the symmetrical key. It is much faster and easier
to use.
--
--- Nick Malik [Microsoft]
MCSD, CFPS, Certified Scrummaster
http://blogs.msdn.com/nickmalik
Disclaimer: Opinions expressed in this forum are my own, and not
representative of my employer.
I do not answer questions on behalf of my employer. I'm just a
programmer helping programmers.
--
"Ray Cassick (Home)" <rc************ @enterprocity.c om> wrote in
message news:%2******** **********@TK2M SFTNGP09.phx.gb l...
> Ok, time to ask the question here.. I have been battling over this
one for > sometime now and just have to ask it.
>
> I have created a few classes that I use to act a security keys.
These > classes get serialized using a binary formatter and then
symmetrically > encrypted. The app will deserialize them and use the contents to
judge > licensing capabilities, etc.
>
> Currently the license key and vectors are stored in the code. I
don't like > the idea simply because it allows someone with a decompile to get at
them. > Yes, I can obfuscate the code but being paranoid like I am I have a
feeling
> that is just not enough.
>
> My real biggest fear besides the fact that someone can use the key
to > decrypt the data is that someone can also use the same key to create
a > program that will generate fake license keys for my app.
>
> In another case I have to send a class across a wire on a remoting
channel > and the class is going to have a users name and password in it.
Again, being
> the paranoid programmer that I am I am really afraid of someone with
a > sniffer out there looking at the raw bits. I would like to encrypt
the > password before I send the class across the wire. Again, I know that
I can > just hard code the keys into the app but we all know what I feel
about that.
>
> I know that I could use asymmetrical encryption and that gives me
the > ability to release a public key that can only be used to decrypt and
that > takes care of part of it but from what I have seen asymmetrical
encryption > is a royal pain in the butt because it only encrypts data of a
maximum size
> so I would have to take that into account when I am serializing data
and > possibly split the data up into checks, each one encrypted.. Not a clean > option really.
>
> I know already, I have read tones of thing on remoting and how to build > encryption sinks to be used for cases like this, but I really don't need to
> encrypt the entire message, just one part of it.
>
> There HAS to be a way to reliably use symmetrical encryption without
hard > coding the keys into the code but also protecting them from being
used by > other people.
>
> Any simple ideas to this tough question?
>
>
William Stacey [MVP] wrote: Hey Sean. Just curious. How are you protecting the license so that
it is unique the user and can not be emailed to another user? Using a
machine hash or something and signing that with the rest of the license?
What do you include in your machine hash?
In my currently posted code, I've just used the machine name. The
release I'm working on also allows for domain name, user name, primary
Cpu ID, primary MAC address, and a whole bunch of other variables (both
manually entered and automatically generated). Which ones you want are
set by a policy. The license file contains these values in the clear
currently. Since the license file comes back signed with those values
in them, I don't feel that hashing is required, since any tampering
with the values will invalidate the license file.
I'm also trying to make the whole scheme extensible. The default Policy
works off a signed policy file, but you can implement your own Policy
classes if you want. Basically I'm aiming for a sort of Licensing
Application Block. Any ideas will be welcomed, you can view my email
address at http://home.imaginet.co.za/codingsan...ages/email.jpg.
Don't use this one I posted with, it's just spambait ;D.
I'd also like to implement a license server, license tracking system,
and various other goodies (but that might take a while). As usual, I
started working on this as just a simple licensing system for a little
commercial app I wrote for a friend and it just sort of ballooned out
of control ;D
I'll blog about improvements and releases as I make them.
Currently, you can't round-trip a XenoCode'd assembly. This may
change in the future with a new version of ildasm, but can't today. TIA
Interesting about XenoCode, does anyone have any idea how they crash
ILDASM?
In any case my licensing system is not meant to be a replacement for
top-quality systems like that and XHEO, but rather a decent-quality
system with enough features to be useful, and extensible enough to be
flexible. Good enough to stop someone with a bit of knowledge with
registry and XML, but not enough to stop someone with the ability to
roundtrip. Of course, if someone can let me know how to crash ILDASM,
then I'll happilly add that functionality in. Assuming it doesn't
violate any patents of course.
Sean Hederman http://codingsanity.blogspot.com This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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Ok, time to ask the question here.. I have been battling over this one for
sometime now and just have to ask it.
I have created a few classes that I use to act a security keys. These
classes get serialized using a binary formatter and then symmetrically
encrypted. The app will deserialize them and use the contents to judge
licensing capabilities, etc.
Currently the license key and vectors are stored in the code. I don't like
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