>Anyone knows how to make a key from a string.
>
>I have a key ( string ) which I want to use for a RC4 encryption. The problem I have is to set up a key (using CryptImportKey() I guess). Once I have set up the key I can call either CryptEncrypt() or CryptDecrypt().
>
>I am generating a small pdf file which I would like to protect from modifying
>
>Now I have a little program in vfp that does the RC4 encryption ( rc4(rc4Key, src) ). I would prefer to use the crypto functions instead since they will be much faster.

I'm not sure I understand your problem.
Does this help?

oCrypto = NEWOBJECT("_cryptapi",HOME() + "ffc\_crypt.vcx")
cEncryptedStream=SPACE(255)
oCrypto.EncryptSessionStreamString(cEncryptedString, cPassWord, @cEncryptedStream)
* now cEncryptedStream has your encrypted string.

If what you are looking for is to encrypt a whole pdf file, then you could use something like this:

oCrypto = NEWOBJECT("_cryptapi",HOME() + "ffc\_crypt.vcx")
oCrypto.encryptsessionstreamfile("temp\test.pdf",cPassWord,"test.pdf.enc")
* now you have a resulting, encrypted file (original is left untouched)
* this will reverse it:
oCrypto.decryptsessionstreamfile("test.pdf.enc",cPassWord,"test.pdf")

HTH