digital signature

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digital signature

[′dij·əd·əl ′sig·nə·chər]
(communications)
A set of alphabetic or numeric characters used to authenticate a cryptographic message by ensuring that the sender cannot later disavow the message, the receiver cannot forge the message or signature, and the receiver can prove to others that the contents of the message are genuine and originated with the sender.

digital signature

(cryptography)
Extra data appended to a message which identifies and authenticates the sender and message data using public-key encryption.

The sender uses a one-way hash function to generate a hash-code of about 32 bits from the message data. He then encrypts the hash-code with his private key. The receiver recomputes the hash-code from the data and decrypts the received hash with the sender's public key. If the two hash-codes are equal, the receiver can be sure that data has not been corrupted and that it came from the given sender.

digital signature

A digital signature is the electronic equivalent of a person's physical signature. It is also a guarantee that information has not been modified, as if it were protected by a tamper-proof seal that is broken if the contents were altered.

Signed Certificates
Digitally signed certificates verify the identity of an organization or individual. Signed certificates are widely used to authenticate a website and establish an encrypted connection for credit cards and confidential data (see digital certificate, SSL and TLS).

Signed Files
Files of any kind can be signed; however, a common application is "code signing," which verifies the integrity of executables downloaded from the Internet. Code signing also uses certificates (see code signing and digital certificate).

An Encrypted Digest
A digital signature is actually an encrypted digest of the data being signed. The digest is computed from the contents of the file by a one-way hash function (see below) and then encrypted with the private key of the signer's public/private key pair. To prove that the file was not tampered with, the recipient uses the public key of the signer to decrypt the signature back into the original digest, recomputes a new digest from the transmitted file and compares the two to see if they match. If they do, the file has not been altered in transit by an attacker. See RSA, MD5, SHA, public key cryptography and electronic signature.


An Encrypted Digest
A digital signature is an encrypted digest of a file. The digest was created with a one-way hash function from the file's contents.







With and Without Privacy


The following two diagrams show how digital signatures are used for data integrity in both non-private and private transmissions.


Message Integrity Without Privacy
The woman makes her message tamper proof by encrypting the digest into a "digital signature," which accompanies the message. At the receiving side, the man uses her public key to verify the signature. However, the message text is sent "in the clear" and could be read by an eavesdropper.








Message Integrity With Privacy
In this example, the message is both signed and transmitted in secret. The woman signs the message first and then entirely encrypts it before sending. The man decrypts the message first and then verifies the signature.
References in periodicals archive ?
Arcot Systems' Universal Client digital signing system, a multi-layered authentication and digital signature technology, was chosen by AstraZeneca to manage the most elusive of all the elements, the digital signature.
This service also protects against phishing by using client authentication to prevent unauthorized access and digital signing to confirm sources.
By embedding Arcot technology into these applications, Adobe gave its users the framework for secure digital signing, anywhere, anytime, without the need for additional software or hardware.
This award validates our strategy of solving our customers' problems by providing authentication and digital signing solutions that deliver the right balance of security, cost and convenience.
Incorporating a true random number generator, miniHSM offers secure cryptographic key provisioning and storage, and a built-in real-time clock enables value-added functionality such as time-stamping in addition to the standard cryptographic functions of encryption, digital signing and authentication.
Frost & Sullivan, a global growth consulting company, recognized Arcot for its development of the ArcotID(R), a unique software-only solution for electronic strong authentication and digital signing.
com) to offer Web-based digital signing capability and secure document delivery.
today announced a collaboration with Adobe Systems Incorporated to enable a new option for digital signing in Adobe(R) Acrobat(R) software and Adobe Reader(R) software using easy-to-use "Roaming Digital IDs.
It provides strong user authentication and cost-effective password management solutions enabling organizations to easily and effectively expand business opportunities with secure network access, improve data security through enhanced encryption and digital signing, and reduce costs and vulnerabilities through superior password management.
The alliance is focused on the integration of Arcot's universal digital signing solution with the EMC Documentum enterprise content management (ECM) platform.
SafeNet's DRM Fusion Toolkit includes cryptography algorithms, digital signing, authentication, certificate management, secure licenses and communication protocols to content and service providers.

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