Instruct: Given a question, retrieve passages that can help answer the question.
Query: What is encryption?
In cryptography, encryption is the process of encoding a message or information in such a way that only authorized parties can access it and those who are not authorized cannot. Encryption does not itself prevent interference, but denies the intelligible content to a would-be interceptor. In an encryption scheme, the intended information or message, referred to as plaintext, is encrypted using an encryption algorithm – a cipher – generating ciphertext that can be read only if decrypted. For technical reasons, an encryption scheme usually uses a pseudo-random encryption key generated by an algorithm. It is in principle possible to decrypt the message without possessing the key, but, for a well-designed encryption scheme, considerable computational resources and skills are required. An authorized recipient can easily decrypt the message with the key provided by the originator to recipients but not to unauthorized users.
Functional encryption is a generalization of public-key encryption in which possessing a secret key allows one to learn a function of what the ciphertext is encrypting.
Assuming that a deterministic encryption scheme is going to be used, it is important to understand what is the maximum level of security that can be guaranteed.
Section 84A of the Indian Information Technology (Amendment) Act, 2008 empowers the government to formulate rules on modes of encryption for the electronic medium. Legal commentators have noted the lack of transparency about what types of encryption use and deployment are permitted and required under Indian law, especially in the field of electronic communications services. Thus, the Central Indian Government has, in theory, a broad exclusive monopoly over electronic communications which includes the privilege to provide telecommunication and Internet services in India.
The message key is three characters long, so the doubled key is six characters long. Rejewski labeled the permutations for the successive message-key characters "A B C D E F". He did not know what those permutations were, but he did know that "A" and "D" permutations encrypted the same message key letter, that "B" and "E" encrypted the same letter, and that "C" and "F" encrypted the same letter. If are the (unknown) plaintext letters of the message key and are the corresponding (known) ciphertext letters, then
"Share" uses encryption to hide the identity of who is transferring or what they are transferring. It is non-centralized so it cannot be easily shut down and it supports multiple source "swarm" downloading. All files are transferred encrypted so they must be decrypted upon download completion. In the meantime they are stored in encrypted form in a "Cache" folder. This folder is also used to allow recently downloaded files to be shared among the network based on priorities.
Email on the internet is sent by the Simple Mail Transfer Protocol (SMTP). While mail can be encrypted between mail servers, this is not typically enforced, but instead Opportunistic TLS is used - where mailservers negotiate for each email connection whether it will be encrypted, and to what standard. Where a mail flow between servers is not encrypted, it could be intercepted by an ISP or government agency and the contents can be read by passive monitoring. 
For higher security, email administrators can configure servers to "require" encryption to specified servers or domains. 
IBCPRE supports one-to-many encryption. The data owner Alice can choose multiple friends to share her data with. For multiple friends to share the encrypted messages with, Alice simply needs to generate a re-encryption key for each of her friends and sends all the re-encryption keys to the server for carrying out the re-encryption. The number of re-encryption keys that Alice needs to generate depends on the number of friends that Alice wants to share the encrypted messages with. It does not depend on the number of encrypted messages. One re-encryption key will allow the Server to convert all the encrypted messages provided the tag of the encrypted messages and the tag of the re-encryption key matches.
In an address to the 2016 South by Southwest conference on March 11, President Barack Obama stated that while he could not comment on the specific case, "You cannot take an absolutist view on [encryption]. If your view is strong encryption no matter what, and we can and should create black boxes, that does not strike the balance that we've lived with for 200 or 300 years. And it's fetishizing our phones above every other value. That can't be the right answer."
Disk encryption does not replace file encryption in all situations. Disk encryption is sometimes used in conjunction with filesystem-level encryption with the intention of providing a more secure implementation. Since disk encryption generally uses the same key for encrypting the whole drive, all data is decryptable when the system runs. However, some disk encryption solutions use multiple keys for encrypting different volumes. If an attacker gains access to the computer at run-time, the attacker has access to all files. Conventional file and folder encryption instead allows different keys for different portions of the disk. Thus an attacker cannot extract information from still-encrypted files and folders.
There are a number of limitations on the free deployment of encryption by electronic communications services despite the fact that Indian law and policy promotes and requires the implementation of strong encryption as a security measure, such as in banking, ecommerce and by organizations handling sensitive personal information. There is notable legal uncertainty about the precise legal scope of these license requirements and to what extent they could have legal effect on (the use of or deployment of ) services by the end-users of covered services. The encryption debate ignited publicly in India in 2008 after the Government published a draft proposal with a number of envisioned limitations on the use of encryption. The policy, issued under Section 84A of the Indian Information Technology (Amendment) Act, 2008 was short-lived, but worries remain about the lack of safeguards for privacy and freedom of expression that the draft illustrated. In response to the outcry, the Indian government first exempted ""mass use encryption products, which are currently being used in web applications, social media sites, and social media applications such as Whatsapp, Facebook, Twitter etc."" Soon thereafter, it withdrew the proposed policy and a new policy has not been made public yet.
In 1970, James H. Ellis, a British cryptographer at the UK Government Communications Headquarters (GCHQ), conceived of the possibility of "non-secret encryption", (now called public key cryptography), but could see no way to implement it. In 1973, his colleague Clifford Cocks implemented what has become known as the RSA encryption algorithm, giving a practical method of "non-secret encryption", and in 1974, another GCHQ mathematician and cryptographer, Malcolm J. Williamson, developed what is now known as Diffie–Hellman key exchange. 
The scheme was also passed to the USA's National Security Agency. With a military focus and low computing power, the power of public key cryptography was unrealised in both organisations:
There is a plurality of terms that are used to describe implementations of disk encryption: on-the-fly encryption (OTFE); full disk encryption (FDE), whole disk encryption; filesystem-level encryption, encrypted filesystem, cryptographic filesystem, etc. All of them refer to an encryption layer in the storage stack. This article describes these techniques and explains their pros and cons. This article does not reference any software or hardware implementing these techniques (see disk encryption software and hardware), and it does not describe cryptographic theory behind it (see disk encryption theory).
Because not all stored data are always sensitive and important, column level encryption was created to allow users the flexibility in choosing what sort of attributes should or should not be encrypted. This is to minimum performance disruption when executing crypto algorithms by moving data in and out of devices.
Column level encryption is a type of database encryption method that allows user to select specific information or attributes to be encrypted instead of encrypting the entire database file. To understand why column level encryption is different from other encryption methods like file level encryption, disk encryption, and database encryption, a basic understanding of encryption is required.
The FBI–Apple encryption dispute concerns whether and to what extent courts in the United States can compel manufacturers to assist in unlocking cell phones whose data are cryptographically protected. There is much debate over public access to strong encryption.
Each file is encrypted in blocks, and this option controls what size those blocks are. Each time a single byte is read the entire block it is contained in must be decrypted. Likewise, for each write the block must be decrypted, altered, and re-encrypted.
Disk encryption generally refers to wholesale encryption that operates on an entire volume mostly transparently to the user, the system, and applications. This is generally distinguished from file-level encryption that operates by user invocation on a single file or group of files, and which requires the user to decide which specific files should be encrypted. Disk encryption usually includes all aspects of the disk, including directories, so that an adversary cannot determine content, name or size of any file. It is well suited to portable devices such as laptop computers and thumb drives which are particularly susceptible to being lost or stolen. If used properly, someone finding a lost device cannot penetrate actual data, or even know what files might be present.
The apparatus includes a pad, an encrypting circuit that is adjacent the pad and a link coupling the pad and the encrypting circuit. The pad is for entering an identifier, and the circuit for encrypting the entered identifier. The pad may be a physical touch pad such as an N-wire technology touch pad. Alternatively, the pad may be a virtual touch screen. The encrypting circuit may be a CPU along with a memory coupled to the CPU and programmed to encrypt. The CPU and programmed memory may be the first CPU programmable to encrypt the entered identifier, through which the identifier passes. The encrypting circuit may be a micro controller programmed to encrypt. In still another variation, the encrypting circuit may be an application-specific integrated circuit (ASIC). The apparatus may include a housing that encloses the encrypting circuit and link. The housing would be resistant to access, tampering or tapping. The housing may be at least partially of chip-on-glass technology. The encrypting circuit may be embedded in the housing, as may the link. A method for encrypting an identifier includes placing a pad for entering an identifier, a circuit for encrypting an identifier and a link communicative coupling the pad and the circuit adjacent in an access-resistant housing. An identifier is entered on the pad and communicated to the encrypting circuit. The encrypting circuit encrypts the identifier. The encrypted identifier may be forwarded for verification.
There are two alternatives to ISMACryp, SRTP and IPsec, that can also be used to provide service and content protection. The difference between the three is at what level encryption is done. Whereas ISMACryp encrypts MPEG-4 access units (that are in the RTP payload), SRTP encrypts the whole RTP payload, and IPsec encrypts packets at .
Disk encryption refers to encryption technology that encrypts data on a hard disk drive. Disk encryption typically takes form in either software (see disk encryption software) or hardware (see disk encryption hardware). Disk encryption is often referred to as on-the-fly encryption (OTFE) or transparent encryption.
To prevent unauthorized users from using or potentially interfering with the military signal through spoofing, it was decided to encrypt the P-code. To that end the P-code was modulated with the "W-code", a special encryption sequence, to generate the "Y-code". The Y-code is what the satellites have been transmitting since the anti-spoofing module was set to the "on" state. The encrypted signal is referred to as the "P(Y)-code".
With full disk encryption, the entire disk is encrypted (except for the bits necessary to boot or access the disk when not using an unencrypted boot/preboot partition). 
As disks can be partitioned into multiple partitions, partition encryption can be used to encrypt individual disk partitions. 
Volumes, created by combining two or more partitions, can be encrypted using volume encryption. 
File systems, also composed of one or more partitions, can be encrypted using filesystem-level encryption. 
Directories are referred to as encrypted when the files within the directory are encrypted. 
File encryption encrypts a single file. 
Database encryption acts on the data to be stored, accepting unencrypted information and writing that information to persistent storage only after it has encrypted the data. Device-level encryption, a somewhat vague term that includes encryption-capable tape drives, can be used to offload the encryption tasks from the CPU.
Both XML Signature and XML Encryption use the KeyInfo element, which appears as the child of a SignedInfo, EncryptedData, or EncryptedKey element and provides information to a recipient about what keying material to use in validating a signature or decrypting encrypted data.
Recent incidents of terrorism have led to further calls for restrictions on encryption. Even though, in the interest of public safety, there are many proposals to interfere with the free deployment of strong encryption, these proposals do not hold against close scientific scrutiny. These proposals side-step a more fundamental point, related to what is at stake for users. More advanced security measures seem necessary for governments, considering the existing threat landscape for users of digital communications and computing.