Eli5 bitcoin calculator
Jump to navigation Jump to search Not to be confused with One-time pad. The most important advantage that is addressed by OTPs is that, in contrast to static passwords, they are eli5 bitcoin calculator vulnerable to replay attacks. This means that a potential intruder who manages to record an OTP that was already used to log into a service or to conduct a transaction will not be able to abuse it, since it will no longer be valid.
OTPs have been discussed as a possible replacement for, as well as enhancer to, traditional passwords. On the downside, OTPs are difficult for human beings to memorize. Therefore, they require additional technology to work. OTP generation algorithms typically make use of pseudorandomness or randomness, making prediction of successor OTPs by an attacker difficult, and also hash functions, which can be used to derive a value but are hard to reverse and therefore difficult for an attacker to obtain the data that was used for the hash. There are also different ways to make the user aware of the next OTP to use.
Some systems use special electronic security tokens that the user carries and that generate OTPs and show them using a small display. Other systems consist of software that runs on the user’s mobile phone. It might look like a small calculator or a keychain charm, with an LCD that shows a number that changes occasionally. All of the methods of delivering the OTP below may use time-synchronization instead of algorithms. Each new OTP may be created from the past OTPs used.
The value stored is then replaced by p and the user is allowed to log in. Again, the new value replaces p and the user is authenticated. This can be repeated another 997 times, each time the password will be f applied one fewer times, and is validated by checking that when hashed, it gives the value stored during the previous login. Since f was chosen to be one-way, this is extremely difficult to do. The use of challenge-response one-time passwords requires a user to provide a response to a challenge.
For example, this can be done by inputting the value that the token has generated into the token itself. To avoid duplicates, an additional counter is usually involved, so if one happens to get the same challenge twice, this still results in different one-time passwords. The methods of delivering the OTP which are token-based may use either of these types of algorithm instead of time-synchronization. A common technology used for the delivery of OTPs is text messaging. Because text messaging is a ubiquitous communication channel, being directly available in nearly all mobile handsets and, through text-to-speech conversion, to any mobile or landline telephone, text messaging has a great potential to reach all consumers with a low total cost to implement. On smartphones, one-time passwords can also be delivered directly through mobile apps, including dedicated authentication apps such as Authy, Duo, and Google Authenticator, or within a service’s existing app, such as in the case of Steam.
Recently, it has become possible to take the electronic components associated with regular keyfob OTP tokens and embed them in a credit card form factor. However, the thinness of the cards, at 0. 84mm thick, prevents standard components or batteries from being used. Yubico offers a small USB token with an embedded chip that creates an OTP when a key is pressed and simulates a keyboard to facilitate easily entering a long password. Since it is a USB device it avoids the inconvenience of battery replacement.
A new version of this technology has been developed that embeds a keypad into a payment card of standard size and thickness. The card has an embedded keypad, display, microprocessor and proximity chip. Authentication-as-a-service providers offer various web-based methods for delivering one-time passwords without the need for tokens. One such method relies on the user’s ability to recognize pre-chosen categories from a randomly generated grid of pictures.
In some countries’ online banking, the bank sends to the user a numbered list of OTPs that are printed on paper. Other banks send plastic cards with actual OTPs obscured by a layer that the user has to scratch off to reveal a numbered OTP. For every online transaction, the user is required to enter a specific OTP from that list. Some systems ask for the numbered OTPs sequentially, others pseudorandomly choose an OTP to be entered. This leads to an additional development cost. Use of an existing mobile device avoids the need to obtain and carry an additional OTP generator.
2011 most small card devices do not have rechargeable, or indeed replaceable, batteries. However, most proprietary tokens have tamper-proof features. One-time passwords are vulnerable to social engineering attacks in which phishers steal OTPs by tricking customers into providing one or more OTPs that they used in the past. In late 2005 customers of a Swedish bank were tricked into giving up their one-time passwords.