Cryptography Applications in real life

SIM Authentication :
To decide whether or not the SIM may access the network, the SIM needs to be authenticated
A random number is generated by the operator, and is sent to the mobile device Together with the secret key Ki, this random number runs through the A3 algorithm (it is this Ki that recently has been compromised)

The output of this calculation is sent back to the operator, where the output is compared with the calculation that the operator has executed himself (the operator possesses the secret keys for all SIM cards the operator has distributed)
Encryption :
This part is the part that has been cracked. In short, the operator generates a random number (again), and sends it to the mobile phone. Together with the secret key Ki, this random number runs through the A8 algorithm, and generates a session key KC. This KC is used, in combination with the A5 algorithm to encrypt/decrypt the data.
note : A5,A8,A3 are algorithms used
Whatsapp Encryption:

‘Whatsapp’ is currently one of the most popular mobile messaging software. It is available for different platforms such as Android, Windows Phone, and iPhone. ‘Whatsapp’ also enables users to make free calls with other users. In the latest version of ‘Whatsapp,’ the conversations and calls are “end-to-end” encrypted.
What does end-to-end encryption mean?
In end-to-end encryption, only the data is encrypted. The headers, trailers, and routing information are not encrypted. End-to-to end encryption in Whatsapp has been developed in collaboration with ‘Open Whisper Systems.’
End-to-end encryption makes sure that a message that is sent is received only by the intended recipient and none other. Whatsapp has ensured, that even “it” cannot read the messages making itself a very strong messaging platform. It also means that outsiders or third party individuals cannot snoop on conversations between intended recipients as well.
How is end-to-end encryption in Whatsapp implemented?
Whatsapp end-to-end encryption is implemented using asymmetric cryptography or public key systems. Recall, that in asymmetric encryption, when one key is used to encrypt (here, the public key), the other key is used to decrypt (here, the private key) the message.
Once ‘Whatsapp’ is installed on a user’s smartphone, the public keys of ‘Whatsapp’ clients are registered with the Whatsapp server. It is important to note here that the private key is not stored on Whatsapp servers.
Mobile Banking :
Mobile Banking Authenticating users over the phone or on website is the most important factor for any business, where transactions are carried out using insecure Internet channel. The modern communication medium is very much exposed to various threats. One time password (OTP) is used to prove one‟s identity over the wireless channel. The user can receive the OTP via text message.

OTP SMS which is one of the Smart way of sending a Pin, is a system to send to anyone‟s mobile phone a “one time password” for their money transfer and payment operations and Internet Banking login. The OTP generated is encrypted using the powerful AES algorithm. The generated OTP value is encrypted using powerful AES algorithm and sends it to users.
Although OTPs are in some ways more secure than a static memorized password, users of OTP systems are still vulnerable to fraudulent attacks. OTPs should therefore not be disclosed to any third parties, and using an OTP as layered security is safer than using OTP alone; one way to implement layered security is to use an OTP together with a password that is exclusively with the the user (and never transmitted to the user, as OTPs often are).
Digital signatures

Having seen how encryption is implemented in Whatsapp, let us see the next practical application of cryptography — Digital signatures. Digital signatures are signatures applied digitally. They enforce the concepts of authentication, non-repudiation, and confidentiality. Wikipedia defines digital signatures the following way: “A digital signature is a mathematical scheme for demonstrating the authenticity of a digital message or documents.”
If you receive a message from me that I have encrypted with my private key and you are able to decrypt it using my public key, you should feel reasonably certain that the message did in fact come from me. If I think it necessary to keep the message secret, I may encrypt the message with my private key and then with your public key, that way only you can read the message, and you will know that the message came from me. The only requirement is that public keys are associated with their users by a trusted manner, for example a trusted directory. To address this weakness, the standards community has invented an object called a certificate. A certificate contains, the certificate issuer’s name, the name of the subject for whom the certificate is being issued, the public key of the subject, and some time stamps. You know the public key is good, because the certificate issuer has a certificate too
Device Locking

Mobile devices and the data they contain are frequently protected by locking 11 mechanisms that ensure, by default, that phone data is encrypted whenever the screen is locked and that only the user can unlock the phone and its contents. For phones, this combination of cryptographic passcode protection and full disk encryption was introduced as the default setting in Apple’s iOS 9 and Android’s Marshmallow system, although not all vendors of Android phones implement this encryption.
Just don’t be afraid about studying on cryptography .Use it and learn it
