Any one with complete knowledge of the data stream can generate a correct sum, a more secure approach is to use a keyed-hash like HMAC which requires knowledge of a secret key to generate thereby providing data authenticity in addition to integrity. A simple approach to integrity is to append an MD5 or SHA-1 sum at the end, but that only provides data integrity, not data authenticity. An attacker can easily guess that an SSL connection to port 443 is probably a webpage request starting with GET / and he could flip bit changing it to PUT / without interfering with the rest of the encryption. While an attacker may not be able to read data in transit, he may be able to flip bits without detection if no integrity or authenticity is applied to the data stream. Lastly, it's important to verify the data you are receiving. These modes specify how to encrypt a stream of bits using a block mode cipher. To encrypt more than a block, you must use a Mode of Operation like CBC or CTR. DES uses 64-bit blocks and AES uses 128-bit blocks. They only encrypt data in block of a specific size. The full standard for RSA is called PKCS #1įurthermore, DES and AES are block ciphers. Then anyone which access to the private key can extract the symmetric key and decode the message with AES. You can generate a random 256 bit key for AES and encrypt that key with a 1024 bit RSA public key. This is one of the reasons, RSA is used in combination with a symmetric key cipher like DES or AES. ![]() When you talk about a RSA key that's 1024 bits, that means it takes 1024 bits to store the modulus in binary. ![]() Specifically, an integer from 0 to n-1 where n is the modulus value from the public key. RSA isn't designed to encrypt any arbitrary string, it's an algorithm that encrypts an integer. But if your experimenting and just want to learn how it works, you need to understand what RSA is. First, if you just want good encryption, you should look at GnuPG.
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