Q: Add wodCrypt to my project?
1. Install the product using wodCrypt.EXE setup package.
2. In VB IDE, open your project (or create new)
3a. Go to menu 'Project', then select 'Components', find 'WeOnlyDo! COM Crypt ActiveX Control', click on it and select 'OK'
3b. Find wodCrypt's small icon on toolbox, drag it and drop it to your form
... or, if you prefer to use COM object (slightly faster) ...
3a. Go to menu 'Project', then select 'References', find 'WeOnlyDo! COM Crypt Component', click on it and select 'OK'
3b. Open your code, find (General)(Declarations) and add this line:
Dim WithEvents Crypt1 As wodCryptCom
3c. In Form_Load sub add this line as well
Set Crypt1 = New wodCryptCom
Q: Encrypt a file?
' declare blob object that will keep our files
Dim infile As FileBlob
Dim outfile As FileBlob
' open original file
Set infile = New FileBlob
infile.FileName = "c:\test.txt"
' create output file
Set outfile = New FileBlob
outfile.FileName = "c:\test.enc"
' select cipher
Crypt1.Type = AES
' set password
Crypt1.SecretKey = "my secret password"
' and, finally, encrypt it
Crypt1.Encrypt infile, outfile
' destroy infile and outfile objects
' so file handles are released
Set infile = Nothing
Set outfile = Nothing
Q: Decrypt a file?
Decrypt is very similar to encrypt. In above (Encrypt) snippet, replace
Crypt1.Encrypt infile, outfile
with
Crypt1.Decrypt outfile, infile
You might want to change filenames, so original test.txt you started with doesn't get overwritten!
Q: Encrypt text?
This is basically the same as encrypting files, except you might want to use MemBlob instead of FileBlob.
Also, since encrypted text is containing binary data, you might want to use BASE64 encoding of resulting text. So, you can try something like this:
' declare blob object for our text
Dim intext As New MemBlob
Dim outtext As New MemBlob
' feed original file
intext.Text = "This is the text I want to protect"
' select cipher
Crypt1.Type = AES
' set password
Crypt1.SecretKey = "my secret password"
' and, finally, encrypt it
Crypt1.Encrypt intext, outtext
' show me what we got
Debug.Print outtext.ToBase64
Kf///95IIxi+Z4RK4c3NzXYqR0YyWl//8gMpZcUtjgySDVtkjLVQXJD1JJUeomi2kUgh31b4GF0N1Wg4hMIW3A==
Q: Decrypt text?
Same sample as above, just replace Encrypt with Decrypt, and swap intext and outtext.
Q: Create my own private key to sign a document?
You can use our wodKeys component to create, load and save private (and public) keys.
Creating new private key (that is used to Sign data) is as easy as this:
Dim key As New Keys
key.Generate RSAkey
key.Save "c:\mykey.rsa", "some password"
Once key is generated, you should NEVER send it to anyone - it is your only and you should keep it in the safe place!!
If someone wants to verify your signature, you should use key.PublicKey property to get your public key and send it to that person.
Public keys are derived from private ones, and can be used by 3rd party to verify your signatures -
but they can never be used to sign other documents, pretending to be you!
Q: Sign the document
Your document can be either stored in some file (in which case you would use FileBlob as in above Encrypt snippet),
or can be in some variable (in which case you might want to use MemBlob and populate it through MemBlob.Text property).
You must know that making Signatures is very time consuming process! You should *never* try to sign real documents.
Rather, you should create MD5 or SHA1 digest values of your documents, and then sign those.
It is much faster to sign 16-20 bytes, than few (hundred) kilobytes.
Prepare your private key for this! You can look above to see how to generate it.
So, try something like this:
' declare blob object that will keep our files
Dim infile As New FileBlob
Dim hash As MemBlob
Dim outtext As New MemBlob
' feed file that should be signed
Set infile = New FileBlob
infile.FileName = "c:\test.txt"
' initialize output blob to store hash (15-20 chars) value
Set hash = New MemBlob
' initialize output blob to store signature
Set outtext = New MemBlob
' select cipher for making hash
Crypt1.Type = MD5
' create hash
Crypt1.Digest infile, hash
' select cipher for making signature
Crypt1.Type = RSA
' load your private key
Dim key As New Keys
key.Load "c:\mykey.rsa", "some password"
' feed your private key to wodCrypt
Crypt1.SecretKey = key
' and, finally, sign it
Crypt1.Sign hash, outtext
' look what we got
Debug.Print outtext.ToBase64
DDLqG8lFsJGcasy1ZZYP1SD6yY5PsODAjL+b0N3ZHuImDPf6pSaer06uTE/rnzTyAn
MJD4C+/KvJE5H2AfXuLdKRMijBj4nfiCFpLTovgUhfEUniQd8hflaFgMeveGH1SVtC
TBOnIKLUZ/+XZw4F3oFq6I816unPLKQegxtIHNg=
Q: Verify signature on the document
To verify signature, you need the copy of the document, signature data supplied by the person who signed it,
and his public key. Make sure public key really belongs to the person, otherwise you might verify forged signature
with a forged public key - and get successful result!
If you're sure you have real public key, you can try to use code like this:
( I assume here publickey variable has valid public key!)
' declare blob objects
Dim infile As New FileBlob 'original file
Dim hash As MemBlob 'temporary hash
Dim signature As MemBlob 'signature received from the other party
' feed original file
Set infile = New FileBlob
infile.FileName = "c:\test.xml"
' initialize output blob to store hash (15-20 chars) value
Set hash = New MemBlob
' select cipher for making hash
Crypt1.Type = MD5
' create hash
Crypt1.Digest infile, hash
' select cipher for making signature
Crypt1.Type = RSA
' feed signature
Set signature = New MemBlob
signature.FromBase64 ("DDLq........6unPLKQegxtIHNg=")
' set owner's public key
Crypt1.SecretKey = publickey
' now verify the signature
If (Crypt1.Verify(hash, signature) = True) Then
MsgBox "Signature is valid!"
Else
MsgBox "Signature is forged!!"
End If
