Encryption And Decryption In Network Security Pdf
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Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. For most of recorded history, encryption has been used to protect the secrecy of communications between a sender and a receiver.
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Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. For most of recorded history, encryption has been used to protect the secrecy of communications between a sender and a receiver. Governments have historically been heavy users of encryption. The Caesar cipher goes back to the Roman Empire. Ciphers were used by both sides in the American Revolutionary War.
Histories of World War II dwell at length on the contribution of defeating German and Japanese encryption systems to the Allied victory. At the same time, the Allies also relied on encryption systems, some of which were defeated by Axis codebreakers. In recent years, encryption has become far more widely available on a wide range of consumer and business products and services.
Increasingly, encryption is available by default—often without the user even being aware of it—and the keys for decrypting data are held by individual users. As a result, more data is routinely encrypted today than ever before. Today, encryption protects the communications of individuals and organizations from unsophisticated and sophisticated criminals and repressive governments.
It assures the security of electronic commerce transactions over the Internet—for example making it possible to transmit credit card numbers. It protects information stored on smartphones, laptops, and other devices. Encrypted communication capabilities are built into major computing platforms and in an array of messaging applications that are used by hundreds of millions of users.
Computer and communications systems use cryptography for three broad purposes—to protect the confidentiality of information i. Applications that require the secrecy of large volumes of information use symmetric cryptography. Asymmetric public key cryptography is frequently used to securely disseminate keys that are used in symmetric cryptography. For example, cryptography enables the secure distribution of regular software updates, including security patches, over a network and is used to verify the identity of individuals and organizations.
This report focuses largely on the first application, encryption protecting confidentiality. However, it touches on another use of cryptography: schemes to provide exceptional access to information stored on smartphones or laptops that are locked with a passcode may involve modifications to the cryptography that implements the locking mechanism.
The increased availability and use of encryption—most notably to protect access to data stored on smartphones and to keep Internet messages confidential—means that it is increasingly encountered in investigations by law enforcement and intelligence agencies. This chapter provides a basic introduction to encryption and its uses. It provides context for subsequent discussions of mechanisms that would afford government access and associated technical and operational risks.
It begins with a description of the different kinds of encryption that are important today and with an overview of the ways that encryption systems are created.
It then provides an overview of some of the ways that modern computer and communications systems use encryption to provide a secure experience to their end users. This is followed by a description of the issues and challenges of managing the cryptographic keys that encryption systems rely on. The chapter concludes with a discussion of the threats that modern encryption systems face and attempt to defeat.
Encryption schemes transform a plaintext message or stored data into a ciphertext in such a way that the ciphertext reveals little or no information about the original plaintext. Encryption schemes have the following three components: a key generation algorithm, an encryption algorithm, and a decryption algorithm. The encryption algorithm takes plaintext and an encryption key as input and returns a ciphertext.
The decryption algorithm takes as input a ciphertext and a decryption key and returns the plaintext. In a symmetric scheme, the encryption and decryption keys are the same and must be kept secret.
Without the secret key, there is no practical way to decrypt the data. One can visualize the symmetric encryption process as putting plaintext data in a box and then locking the box using a secret key. The box can be opened only using the same secret key. Provided that one uses a suitable algorithm, a properly engineered implementation, and a sufficiently long key, the encryption is unbreakable Box 2.
A physical box can be forced open with tools. By contrast, breaking encryption requires trying each possible key until the correct one is found; this can take an extremely long time. Knowing including guessing or stealing the key is the only practical way to retrieve the data unless one can circumvent the encryption by obtaining the information before it is encrypted or after it is decrypted unless a flaw in the encryption software or cryptographic algorithm can be found and exploited.
In an asymmetric or public-key encryption scheme, the encryption and decryption keys are different, and only the decryption key must be kept secret. The encryptor uses one key, called a public key, while the decryptor uses a different key, called a private key. As the name suggests, the public key is public and enables anyone to encrypt messages. Only the corresponding private key can decrypt the resulting ciphertexts. One can visualize the public-key encryption process as placing the data in a box that locks as soon as one closes the lid.
Anyone can create such a box and lock it, but only someone in possession of the secret key can unlock the box. As with symmetric encryption, knowing the key is the only practical way to retrieve the data, unless one can steal the key or obtain the information before it is encrypted or after it is decrypted. Under some circumstances, encryption schemes may provide for authorized third-party access to encrypted information.
Following a National Research Council report on encryption, this report uses the phrase exceptional access to. Stress that the situation is not one that was included within the intended bounds of the original transaction, but is an unusual subsequent event.
Exceptional access refers to situations in which an authorized party needs and can obtain the plaintext of encrypted data for storage or communications. Government exceptional access refers to the case in which government has a need for access to information under specific circumstances authorized by law. Exceptional access also applies in a business context, where an employer can access information encrypted by an employee, and in an end-user context, such as data recovery after an encryption key is lost.
The design and standardization of secure encryption algorithms is a challenging task. Although there are encryption algorithms that are perfectly secure in the sense that they are unbreakable, 3 these schemes are rarely deployed in the real world because they are not practical.
Even though the encryption schemes that are deployed in practice are not perfectly secure, their security is supported by a rigorous design process backed by a mathematically sound framework that allows cryptographers to carefully study and analyze their strengths and weaknesses.
The process of reviewing and assessing the security of symmetric encryption schemes with the aim of endorsing a scheme as a standard for broad use in the United States and in much of the world generally occurs through a world-wide competition to which experts in symmetric encryption submit their designs.
The algorithms are then cryptanalyzed i. Wide adoption of resulting algorithms, such as occurred with AES, results in increased security for all.
Encryption and other security functions are performed by cryptographic protocols, which describe how cryptographic algorithms are used to perform the tasks necessary to carry out that function. For example, a protocol for confidential communications must describe how a sender and receiver authenticate each other, how they agree on or establish encryption keys, and how the messages they exchange are encrypted and transported across the network.
The challenge of designing practical and secure encryption is magnified by the fact that encryption algorithms and protocols are notoriously fragile. Even a small and seemingly innocuous change in their design. Cryptography is a very active research field in which new techniques continue to be developed, standardized, and deployed.
For example, the most widely used symmetric encryption method, AES, was standardized in the year A new method for encrypting credit card data, called format-preserving encryption, was standardized in Public-key ciphers designed to withstand quantum computers which—if realized at large scale—would provide powerful new capabilities to attackers seeking to break encryption are only now being developed and are expected to be standardized in the mids.
Such techniques—if their performance can be improved so that they are practical—could reduce, for example, the risk of using cloud computing to process confidential data and would also have implications for government access. One potential consequence of this continuing innovation to consider is whether government policies requiring the use of particular technologies may impede future advances. For example, innovation in the United States might well be inhibited if only a single method of encryption or class of encryption methods were allowed domestically.
See J. This vulnerability is the basis of the Compression Ratio Info-leak Made Easy CRIME exploit against secret Web cookies over connections that use data compression, allowing an attacker to hijack an authenticated session. See A. Lenstra, J. Hughes, M. Augier, J. Bos, T. Kleinjung, and C. Real-world systems use a multitude of keys for many different purposes. Some are used to encrypt messages, some are used to encrypt other keys, and others are used to authenticate messages or users. Most often, encryption is used in the design of secure systems as a way to reduce the amount of information that needs protecting by other means.
By encrypting data, it is possible to render components of a system incapable of compromising the data they process, thus reducing the portion of the system that requires deep security analysis. It is critical to properly manage and secure keys. They must be securely created, stored, distributed, certified, backed up, updated, revoked, and deleted. Keys often have a finite lifetime, determined by their specific usage and their risk of exposure.
Other keys that are used to generate other keys tend to have longer lifetimes often many years and require especially strong protection. It is a best practice to delete all copies of a key when it is no longer needed.
Computer applications, software, and hardware all integrate encryption to accomplish objectives that users value. A single laptop or smartphone today, for instance, commonly deploys encryption in multiple different ways, including in the hardware, the firmware that connects the hardware and the operating system, and a large portion of the software that runs on the device.
Thus a mandate for exceptional access would have to be targeted to specific uses of cryptography where the specifics vary according to the device. This section provides some highly simplified examples of some of these applications and the ways that they depend on encryption; the focus is on giving a sense of the role of encryption rather than full details of its implementation.
Applications that protect a single file or a few files almost always use symmetric encryption to protect the file content. The key for the symmetric encryption system may be entered into the program by the user, derived from a user-supplied password, entered from a hardware token, protected by an asymmetric encryption system in which the symmetric.
If data is encrypted and the key is destroyed, the data becomes inaccessible as if it were erased. In fact, deleting the key is even better than deleting the data because deleting the key renders all copies of the data inaccessible even backups and obviates the need to wipe storage media.
Many modern operating systems support full disk 9 encryption, which protects both user data and system programs from disclosure. As with the file encryption scenario outlined above, the files themselves are protected using symmetric encryption.
Additional protective measures combining operating system software and computer hardware protect the system files from modification so that modified program files cannot, for example, access encrypted data and transfer it to an unauthorized user once it has been decrypted.
Full disk encryption systems are complex.
Encrypting and Decrypting PDF Documents
The Encryption service lets you encrypt and decrypt documents. When a document is encrypted, its contents become unreadable. An authorized user can decrypt the document to obtain access to the contents. If a PDF document is encrypted with a password, the user must specify the open password before the document can be viewed in Adobe Reader or Adobe Acrobat. Likewise, if a PDF document is encrypted with a certificate, the user must decrypt the PDF document with the public key that corresponds to the certificate private key that was used to encrypt the PDF document.
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Encrypting and Decrypting PDF Documents
In cryptography , encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext , into an alternative form known as ciphertext. Ideally, only authorized parties can decipher a ciphertext back to plaintext and access the original information. Encryption does not itself prevent interference but denies the intelligible content to a would-be interceptor. For technical reasons, an encryption scheme usually uses a pseudo-random encryption key generated by an algorithm. It is 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.
Since that time, this paper has taken on a life of its own Does increased security provide comfort to paranoid people? Or does security provide some very basic protections that we are naive to believe that we don't need? During this time when the Internet provides essential communication between literally billions of people and is used as a tool for commerce, social interaction, and the exchange of an increasing amount of personal information, security has become a tremendously important issue for every user to deal with. There are many aspects to security and many applications, ranging from secure commerce and payments to private communications and protecting health care information. One essential aspect for secure communications is that of cryptography.