Digital signature

A digital signature or digital signature scheme is a mathematical scheme for demonstrating the authenticity of a digital message or document. A valid digital signature gives a recipient reason to believe that the message was created by a known sender, and that it was not altered in transit. Digital signatures are commonly used for software distribution, financial transactions, and in other cases where it is important to detect forgery or tampering.

electronic signatures, a broader term that refers to any electronic data that carries the intent of a signature, but not all electronic signatures use digital signatures. In some countries, including the United States, Indiaand members of the European Union, electronic signatures have legal significance.Digital signatures employ a type of asymmetric cryptography. For messages sent through a nonsecure channel, a properly implemented digital signature gives the receiver reason to believe the message was sent by the claimed sender. Digital signatures are equivalent to traditional handwritten signatures in many respects, but properly implemented digital signatures are more difficult to forge than the handwritten type. Digital signature schemes in the sense used here are cryptographically based, and must be implemented properly to be effective. Digital signatures can also provide non-repudiation, meaning that the signer cannot successfully claim they did not sign a message, while also claiming their private key remains secret; further, some non-repudiation schemes offer a time stamp for the digital signature, so that even if the private key is exposed, the signature is valid nonetheless. Digitally signed messages may be anything representable as a bitstring: examples include electronic mail, contracts, or a message sent via some other cryptographic protocol.

Main article: Public-key cryptography

A digital signature scheme typically consists of three algorithms:

• A key generation algorithm that selects a private key uniformly at random from a set of possible private keys. The algorithm outputs the private key and a corresponding public key.
• A signing algorithm that, given a message and a private key, produces a signature.
• A signature verifying algorithm that, given a message, public key and a signature, either accepts or rejects the message's claim to authenticity.

Two main properties are required. First, a signature generated from a fixed message and fixed private key should verify the authenticity of that message by using the corresponding public key. Secondly, it should be computationally infeasible to generate a valid signature for a party who does not possess the private key.

Electrical tape (or insulating tape) is a type of pressure-sensitive tape

used to insulate electrical wires and other material that conduct electricity.
 It can be made of many plastics, but vinyl is most popular, as it stretches
 well and gives an effective and long lasting insulation. Electrical tape for
class H insulation is made of fiberglass cloth.
  




A wide variety of electrical tapes is available; some for highly specialized purposes. Electricians generally use only black tape for insulation purposes. The other colours are used to indicate the voltage level and phase of the wire. (In fact, the coloured tape is referred to as "phasing tape".) This is done on large wire which is available only in black insulation. When wires are phased, a ring of tape is placed on each end near the termination so that the purpose of the wire is obvious. The following table describes this usage.

Tape colour	Usage (US)	Usage (UK – old)	Usage (International – new)
Black	Insulation Low voltage, phase A	Insulation Low voltage, neutral	Low voltage, phase B
Red	Low voltage, phase B	Low voltage, phase A	Sheath, 415 V 3 phase
Blue	Low voltage, phase C	Low voltage, phase C	Low voltage, neutral Sheath, 230 V
Brown	High voltage, phase A		Low voltage, phase A
Orange	High voltage, phase B		Sheath, garden tools
Yellow	High voltage, phase C	Low voltage, phase B	Sheath, 110 V site wiring
Green	Earth ground	Earth
Green with yellow stripe	Isolated ground		Earth
Grey	Low voltage, neutral High voltage, neutral		Low voltage, phase C
White	Low voltage, neutral High voltage, neutra

Insight - How Digital Thermometer works

Digital Thermometers are slowly replacing the conventional mercury thermometer due to the ease of taking reading. People often have the misconception that it contains mercury. Digital Thermometers are mercury free. These thermometers contain thermistor inside the tip which is used to measure the temperature. They provide quick and highly accurate results over the body temperature range.

These thermometers are easy to read with LCD display on them. They are equipped with beep alarm & memory function and can record a wide range of temperature. Doctor’s thermometer which are mostly used can read temperature between 94oF and 105oF (35oC and 42oC). It is three in one thermometer as it can record oral, auxiliary and rectal temperatures. Cap is found at the top of the thermometer, since this part is held away from the body. It is of bright colour and made up of smooth, hard plastic. The main function of this cap is to protect the battery from the outer environmental conditions.Cap is found at the top of the thermometer, since this part is held away from the body. It is of bright colour and made up of smooth, hard plastic. The main function of this cap is to protect the battery from the outer environmental conditions.

The body of the thermometer is made up of the slightly hard plastic as compared to cap. It measures 100.5mm long and the width increases from bottom to the top. The widest part is near the cap and the thinnest part is near the tip. It houses the display screen, electronic circuitry, power button and other parts. The design specifications vary from manufacturing company to company. The push button is used to switch on and off the thermometer. As the button is pressed to start it, a beep signal sounds just for a second to shown that it has turned ON.

The display screen also known as a LCD (Liquid Crystal Display) screen, is rectangular in shape. Normally used screen measures 15.5mm long and 6.5mm wide. The main function of the display screen is to display the temperature measurement in oC or oF. It will first display the last measured reading for 3 seconds and then start flashing. This flashing degree indicates that it is ready to measure the temperature.The circuit of Digital Thermometer is shown in the above image. It is made up of Microcontroller, memory which is embedded in the form of COB IC along with some passive components like capacitor, resistors, sensors, buzzer and switch. The analog value of temperature measured is converted to the digital form by Microcontroller and then displayed on the LCD. If the value of temperature exceeds the highest value then the buzzer makes a sound.

The tip is said as the heart of the thermometer. It is the placed closed to the body part to measure the temperature of the body. The tip of the Thermometer contains thermistor to measure temperature. It is a ceramic semiconductor which is bonded in the tip with temperature sensitive epoxy. It is covered with a cap so to prevent it from the outer world. The cap may be made up of metal or stainless steel. Thermistor is responsible for converting the physical temperature into electrical signals.The above image shows the epoxy coating which contains the thermistor. The wires coming out are visible in the image. The temperature reading in the form of electrical signals is carried via these wires for further processing by the circuitry. Thermistor is a special kind of semiconductor in which the value of resistance changes with the change in temperature. Due to change in resistance value, the output voltage changes and the temperature change is detected.