> David Huang wrote: > > Hi there, > > I need to use the AES symmetric algorithm, RSA algorithm to encrypt > large data string or file, like 300k, or 1M. > right now, I have finished the AES( > CBCPaddedEncryptor/CBCPaddedDecryptor) and RSA(RSAES_PKCS1v15) > algorithms development, but can only encrypt limlited length of data.
AES is a block cipher, RSA is a public key cryptosystem. Although they can both be used to encrypt/decrypt data, they're typically used in very different environments for different purposes. >From what you're writing, it seems you're going to interchange one another. That would be a mistake. Please make a step backward and tell us which problem you need to solve, starting from what you want to obtain, not how. > So, I need to devide those large "string" into blocks. but I do not > know how to determine the sizes of blocks. > for example, we use RSA to encrypt data, if the key size is 512, what > block size I should to choose?, if key size is 2048, what another > block size I should choose? is there any equations in this library > that I can calculate it? You're trying to make improper use of the RSA-PKCSv1.5 scheme. > > for the AES CBC block cipher, should we keep the "iv" and "key" the > same? Definitly not, the IV is typically transmitted in clear, while the key is not, and sometimes not even trasmitted at all. -- Giuliano Bertoletti e-Security Manager Intrinsic - Security Monitoring http://www.intrinsic.it COOL-FIRE: la soluzione Firewall per Windows NT/2000 http://www.symbolic.it/Prodotti/cool-fire.html SYMBOLIC S.p.A. Tel: +39 0521 776180 / Fax: +39 0521 776190
