Just a guess, but a fairly educated one, try setting flen to 1 byte (or even
1 bit) smaller than the key. What I suspect is happening is you are
sometimes trying to encrypt values that are larger than the modulus so
you're getting a modular reduction of the value encrypted.
Joe
----- Original Message -----
From: "Jan Zoellner" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, February 14, 2001 2:25 PM
Subject: RSA Encrypt/Decrypt fails
> Hello,
>
> I have a problem for which I found no real solution in the manual or the
> list archives.
> The basic idea is to encrypt data using RSA_private_encrypt and retrieve
it
> using RSA_public_decrypt. For RSA_private_encrypt, I set flen to
RSA_size()
> to encrypt just one block and decrypt it later. If there is more data, it
> is processed blockwise in a loop.
> RSA_NO_PADDING is used (yeah, I know one shouldn´t do that). For most
> blocks, the decryption works fine. For some block it just doesn´t work. I
> don´t get any error reports, the decrypted data just isn´t what it should
be.
>
> Below you find an excerpt from the code (some NULL checkings and the like
> omitted). What am I doing wrong? Once again: There is no overlapping
memory
> or the like, the process functions properly in most cases, but in some
> cases (it seems to be depending on the data actually!) the routine fails,
> either at encryption or decryption (or even both?).
>
> Ciao
> Jan
> ------------------------------------------------------------
> // get key
> rsaStruct = PEM_read_RSAPrivateKey(fp, NULL, NULL, password);
> // srcLen is original length given as a function parameter
> unsigned long destLen = srcLen;
>
> // Now pad to correct block size, resulting in a destination length of
> // N*RSA_size()
> unsigned long blocklength = RSA_size(rsaStruct);
> destLen = (((destLen - 1)/ blocklength) + 1) * blocklength;
>
> // create destination array
> dest = new unsigned char[destLen];
> memset(dest, 0, destLen);
>
> // create source array
> unsigned char *tmpSrc = new unsigned char[destLen];
> memset(tmpSrc, 0, destLen);
>
> // copy original source data, result is an array of correct length
containing
> // the source and trailing zeroes
> memcpy(tmpSrc, src, srcLen);
>
> // now encrypt blockwise
> for (unsigned long i = 0; i < destLen; i+= blocklength) {
> if (blocklength!=RSA_private_encrypt(blocklength, (tmpSrc+i),
> (dest+i), rsaStruct, RSA_NO_PADDING)) {
> printf("RSA Encrpytion Error.\n");
> delete [] dest;
> delete [] tmpSrc;
> return 0;
> }
> }
>
> // and now decrypt the data again
> // array to contain the decrypted data
> unsigned char *tmpDest = new unsigned char[destLen];
> for (i = 0; i < destLen; i+= blocklength) {
> if (blocklength!=RSA_public_decrypt(blocklength, (dest+i),
> (tmpDest+i), rsaStruct, RSA_NO_PADDING)) {
> printf("RSA Decryption Error.\n");
> delete [] dest;
> delete [] tmpDest;
> delete [] tmpSrc;
> return 0;
> }
> }
> ------------------------------------------------------------
>
> --
> Jan Zoellner - VidSoft GmbH
> eMail: [EMAIL PROTECTED] - Tel: ++49 351 435 34 17
> WWW: http://www.vidsoft.de
>
> ______________________________________________________________________
> OpenSSL Project http://www.openssl.org
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>
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