Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Message Authentication Code shopping experience:
1. Compare - without doubt the biggest advantage that the Message Authentication Code offers shoppers today is the ability to compare thousands of Message Authentication Code at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.
2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about
3. Testimonials - don't know anybody that has bought a Message Authentication Code? Wrong! If the Message Authentication Code is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.
4. Questions - Got a question about Message Authentication Code then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....
5. Reputation - Never heard of the company selling Message Authentication Code? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Message Authentication Code and build up a picture of their reputation for sales, returns, customer service, delivery etc.
6. Returns - still worried that even after all of the above your Message Authentication Code wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.
7. Feedback - happy with your Message Authentication Code then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.
8. Security - check for the yellow padlock on the Message Authentication Code site before you buy, and the s after http:/ /i.e. https:// = a secure site
9. Contact - got a question about Message Authentication Code, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.
10. Payment - ready to pay for your Message Authentication Code, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.
A cryptography
message authentication code (MAC) is a short piece of information used to
authenticate a message. A MAC algorithm accepts as input a secret key and an arbitrary-length message to be authenticated, and outputs a MAC (sometimes known as a
tag). The MAC value protects both a message's
integrity as well as its Authentication, by allowing verifiers (who also possess the secret key) to detect any changes to the message content. A
message integrity code (MIC) is another name for a MAC that is usually used when the acronym "MAC" is defined to mean something else, like when it means Media Access Control in networking contexts.
While MAC functions are similar to cryptographic hash functions, they possess different security requirements. To be considered secure, a MAC function must resist existential forgery under
chosen-plaintext attacks. This means that even if an attacker has access to an
oracle which possesses the secret key and generates MACs for messages of the attacker's choosing, he can "never" guess the MAC for any message that he has not yet asked the oracle about. (Here "never" means, "not without doing an infeasible amount of computation").
MACs differ from
digital signatures, as MAC values are both generated and verified using the same secret key. This implies that the sender and receiver of a message must agree on keys before initiating communications, as is the case with
symmetric encryption. For the same reason, MACs do not provide the property of
non-repudiation offered by signatures: any user who can verify a MAC is also capable of generating MACs for other messages. In contrast, a digital signature is generated using the private key of a key pair, which is asymmetric encryption. Since this private key is only accessible to its holder, a digital signature proves that a document was signed by none other than that holder. Thus, digital signatures do offer non-repudiation.
MAC algorithms can be constructed from other cryptographic primitives, such as
cryptographic hash functions (as in the case of
HMAC) or from block cipher algorithms (OMAC (cryptography),
CBC-MAC and
PMAC (cryptography)).
Example
See also
External links
- RSA FAQ's entry on MACs
- Ron Rivest lecture on MACs
A cryptography
message authentication code (MAC) is a short piece of information used to authenticate a message. A MAC algorithm accepts as input a
secret key and an arbitrary-length message to be authenticated, and outputs a MAC (sometimes known as a
tag). The MAC value protects both a message's
integrity as well as its Authentication, by allowing verifiers (who also possess the secret key) to detect any changes to the message content. A
message integrity code (MIC) is another name for a MAC that is usually used when the acronym "MAC" is defined to mean something else, like when it means
Media Access Control in networking contexts.
While MAC functions are similar to
cryptographic hash functions, they possess different security requirements. To be considered secure, a MAC function must resist existential forgery under chosen-plaintext attacks. This means that even if an attacker has access to an
oracle which possesses the secret key and generates MACs for messages of the attacker's choosing, he can "never" guess the MAC for any message that he has not yet asked the oracle about. (Here "never" means, "not without doing an infeasible amount of computation").
MACs differ from digital signatures, as MAC values are both generated and verified using the same secret key. This implies that the sender and receiver of a message must agree on keys before initiating communications, as is the case with symmetric encryption. For the same reason, MACs do not provide the property of
non-repudiation offered by signatures: any user who can verify a MAC is also capable of generating MACs for other messages. In contrast, a digital signature is generated using the private key of a key pair, which is asymmetric encryption. Since this private key is only accessible to its holder, a digital signature proves that a document was signed by none other than that holder. Thus, digital signatures do offer non-repudiation.
MAC algorithms can be constructed from other cryptographic primitives, such as
cryptographic hash functions (as in the case of HMAC) or from block cipher algorithms (OMAC (cryptography),
CBC-MAC and
PMAC (cryptography)).
Example
See also
External links
- RSA FAQ's entry on MACs
- Ron Rivest lecture on MACs
