Hi Geoff,

This question seems to crop up every now and again, so it has been
added to the wiki. I hope you don't mind. 
http://www.cryptopp.com/wiki/RSA_Cryptography#Key_Encoding

Jeff

On Feb 21, 2:23 pm, Geoff Beier <[email protected]> wrote:
> > My first question is that why key files contents are as above,whereas
> > in the code defined 1024 bits(128 bytes) for modulus n?
> > Why does "key.pv" contain 633 bytes?!
> > And which part is n and wich part is d?
>
> Because the key files are hex encoded and contain more than just the
> modulus. The public key is a DER-encoded subjectPublicKeyInfo
> structure. See RFC 5280 for the structure and RFC 3279 for the
> RSA-specific contents.
>
> The private key file is a DER-encoded PKCS#8 PrivateKeyInfo structure.
> The format of the PrivateKey field in that structure is RSAPrivateKey,
> as defined in PKCS#1. The definition of both of those is available
> from RSA here:http://www.rsa.com/rsalabs/node.asp?id=2124
> in the PKCS#8 and PKCS#1 ASN.1 modules, respectively.
>
>
>
> > My second question:
> > Because I want to generate key pair and locate them in two byte
> > arrays, I used of "ArraySink" instead of "FileSink" and changed the
> > above code as below:
>
> Look here:
>
> >                byte* privatekey;
> >                byte* publickey;
>
> and here:
>
> >        CryptoPP::HexEncoder privArray(new
> >            CryptoPP::ArraySink(privatekey,sizeof(privatekey))
> >        ); // Hex Encoder
>
> sizeof(privatekey) is sizeof(byte *). That''s a problem when you then
> tell crypto++ to copy more than sizeof(byte *) into the array :-).
>
> Hope that helps,
>
> Geoff
>
> Ho
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