Cryptography Interview Preparation Guide

The science and art of manipulating messages in order to
make them secure is called cryptography......
types are
symmetric key cryptography and asymmetric key cryptography
1)symmetric key cryptography
same key is used for encryption and decryption
eg :DES IDEA AES
2)Asymmetric key:
public key is used for both encryption and decryption
eg:RSA Difere Hellman

Forgot XP Password
The other day I got a call from a friend who had managed to
remember his administrator password to his Windows XP
computer.

My heart sank as I told him it is almost impossible to
access hi PC now as this was the only account on the
machine, and with no password Windows XP was not going to
let him in!

Forgotten XP Password...

As I stared at my mates computer and asked if he had ever
made a Password Reset Disc I already knew what he was going
to say...

This situation reminded me of asking many friends for their
latest data backup CD/DVD when their computer crashed and
need a rebuild - they NEVER have one!!!

...well a quick check on Google and I found a great service
that could just help my mate out.

This site provides a tool to recover lost Windows XP
passwords - YEAH!

It works very prefect to regain your password .Also use to
bootable CD/DVD or usb

There is a free service as well as a priority service that
will retrieve your passwords within minutes. The fee for
the priority service is very cheap, and is really just to
cover server costs.

a fill - 1/20 per minute
b fill - 1/30 per minute
c can empty - 1/40 per minute


Suppose this take x minute

1 x +1x - 1x
--- -- ---- =1
20 30 40

Solve this x=17(approximately)

If it's the Same Question:
Step 1. (0.1)/18-()/20
Step 2. (0.1)((1/18)-(1/20))
Step 3. 0.1 (10-9)/180 -----------> LCM of 18 & 20 = 180
Step 4. 0.1/180
Step 5. 1/1800 is the Answer
Approx = 0.000557

Yes we can. All the information will be stored in encrypted
form in memory. During fetching, it must be first decrypted
by operating system and then can be read.

Ensuring that various cryptographic keys are provided by
their intended users, and only for their intended purposes,
temper resistent hardware is introduced.

An example temper resistent device is your "SMART CARD".

You have to physically posess the device and also have to
possess the PIN or the password to use it.

those are technics like
face detection
Iris recognition
fingerprint recognition
palm vien recognition.
All these can be used for Authentication

The science of cryptography has existed in one form or
another for centuries.
Cryptography is the art of encoding and decoding messages
for transmission between two
parties, while keeping the message secret from unwanted
viewers. There are many common
implementations of cryptography in use today such as the
HTTPS protocol on the Internet. All
forms of data encryption and cryptography require a key in
some form or another for use in
encoding and decoding data. There are even some modern
methods of encryption that have been
mathematically proven to be unbreakable if they are
implemented properly.
The inherent problem with any form of cryptography is in
the method of key distribution.
To date, all forms of message encryption have possessed
this major vulnerability. As such, it
makes no difference whether a secret message is sent via
homing pigeon, a radio transmission, a
penciled message on a notepad, or whispering to another,
there is no physical way to get a
cryptographic key to another without running the risk of
the key being intercepted.
To solve this dilemma, a radical solution has been proposed
called quantum
cryptography. This method essentially uses photon light
particles to send a key to an intended
recipient. The difference with this method of key
distribution is that it implements quantum
mechanic’s uncertainty principle as a means to guarantee
the privacy of a key during
distribution. Practically, quantum cryptography has the
ability to afford complete privacy during
the entire broadcast of an encoded message.

In quantum computing, we use the concept of qubits,
superposition and coherence. A normal bit can be in only
two states - 0 and 1. But a qubit it can be in 0, 1, or in
the superposition of 0 and 1.


Quantum computers, will be much much faster than
traditional silicon based compuers.

Clipper is a compiler that was well known at the time of
80's and early times of 90's. We can build DOS based
applications (even large applications too) using clipper.
There is no seperate Database required to use
with clipper. It itself is having capacity to maintain data
in the form of tables and we can use it to write coding also.