L03_publickeycrypto

Assume you are use the a single pair of public and

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Unformatted text preview: nt to decrypt the message with your private key. Assume you are use the a single pair of public and private key, (Kpub,Kpriv) Assume for both encryption/decryption and signing/verification. Eve, the attacker, records an encrypted letter sent to you by someone else, and ask you to sign this recorded message (and of course, return the signed c result to her). If you follow Eve’s request and sign on what Eve gives you, you are actually decrypting your own secret letter for Eve. => It’s better to use different public/private key-pairs for different purposes, e.g. one key-pair (Kpub1, Kpriv1) for letting people to send secret to you by (Kpub1, encrypting with Kpub1 and you can decrypt using Kpriv1; use a different pair Kpub1 Kpriv1 use (Kpub2,Kpriv2) for digital-signature/verification, i.e. you use Kpriv2 to sign (Kpub2,Kpriv2) outgoing messages and your intended receiptant can use Kpub2 to verify Kpub2 your signature. your Cube-root attack for e = 3: if m3 < n because the “mod” operation becomes null , Cube-root i.e. m3 mod n = m3 = C and the attacker can obtain m by performing m = 3 C i.e. With e = 3, sending exactly the same secret message to 3 or more people (using With 3 or more public key) would reveal the secret message ; 3 See http://members.tripod.com/irish_ronan/rsa/attacks.html Public Key Cryptography Standard (PKCS) A llist of Standards (PKCS#1 to PKCS#15) on how to use RSA in ist practice, regarding message formatting, information encoding scheme, choice of parameters etc Protected against the following “improper use” or attacks on RSA Protected including: including: Plaintext guessing Chosen ciphertext attack m3 < n Sending the same message to multiple people ; Sending This is done by pre-pending some fixed number of constant and This random bytes to the message to be encrypted/ decrypted random Performance of RSA For hardware implementation, RSA is about 1000 times slower For than DES ; for software implementation, RSA is about 100 times slower ; Time to do RSA decryption on a 1 MIPS VAX was around 30 Time seconds (VERY SLOW…) when it was invented in late 70’s seconds The inventors needed to wo...
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