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Encryption Vulnerabilities

Encryption Vulnerabilities. Confidentiality. Confidentiality is maintained so long as private keys are secure. Authenticity. Authenticity is possible via public-key encryption by encrypting messages twice: E receiverPubKey ( E senderPrivateKey ( message ) ) …more on this later. Integrity.

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Encryption Vulnerabilities

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  1. Encryption Vulnerabilities Confidentiality Confidentiality is maintained so long as private keys are secure. Authenticity Authenticity is possible via public-key encryption by encrypting messages twice: EreceiverPubKey( EsenderPrivateKey( message ) ) …more on this later. Integrity What prohibits alteration of message parts? At the very least such alterations should be obviously detected. Integrity is addressed via …

  2. ciphertext plaintext MD plaintext MD encryption algorithm hash algorithm compare decryption algorithm hash algorithm Cryptographic Hash Functions Calculate a hash value / checksum / message digest based upon the message. The hash algorithm is a one-way function. Message Encoding plaintext Message Decoding ciphertext

  3. block1 block2 block3 ... blockN initial value H chain value H chain value H chain value message digest H H Hashing Algorithms plaintext chain value This H function typically consists of multiple rounds of bitwise logic, parity calculation, word-sized addition, and bit string partitioning/concatenation.

  4. Date Block Size Digest Size Compute Steps in H MD5 1990 512 128 4 rounds of 16 SHA-1 1995 512 160 4 rounds of 20 RIPEMD-160 1996 512 160 4 paired rounds of 16 SHA-512 1995 1024 512 4 rounds of 20 Note that the probability of randomly “guessing” a hash digest of N bits is 1 2N Best Known Hashing Algorithms e.g., the odds of calculating a hash match for a 128-bit checksum are 1 in 264 ≈ 2 * 1019

  5. HMAC (Hashed Message Authentication Code) block size 00…0 key ipad opad + plaintext message + block1 block2 block3 ... blockN hash algorithm hash algorithm 00…0 MD MD The HMAC digest • The HMAC algorithm turns any keyless hashing algorithm into a keyed hash. • The security of the HMAC algorithm depends upon the chosen hashing algorithm. ipad is 00110110 repeated to block length. opad is 01011100 repeated to block length. Note that HMAC is more secure than hashing, because it requires a private key.

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