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 ?
The E-Sign Act defines "electronic signature" in Section 7006(5) as "an electronic sound, symbol, or process, attached to or logically associated with a contract or other record and executed or adopted by a person with the intent to sign the record.
In fact, in 2010, on the 10th anniversary of the E-Sign Act, lawmakers designated June 30 as National E-Sign Day to reaffirm their commitment to "facilitating interstate and foreign commerce in an increasingly digital world.
Las reglas de la UETA y la E-Sign, junto con la aplicacion del principio de equivalencia funcional, facilitan la emision y transmision de los instrumentos negociables al permitir la sustitucion del tradicional documento escrito por un mensaje de datos signado en forma electronica.
The United Nations Commission on International Trade Law has proposed an international convention similar to E-SIGN and UETA, but it may be years before it is accepted globally, Smedinghoff says.
Remember, E-SIGN is technology-neutral, and there are several legally valid eSignature technologies in wide use today.
Currently, neither UETA nor E-Sign requires or mandates electronic transactions or signatures; however, this is not to say that they won't sometime in the future.
To date, e-sign has found its greatest acceptance on federal financial aid documents.
Among the 62 presentations are Business Systems Analysis and Design for RIM Practitioners; RIM Software: Know What You Need to Get What You Want; Managing E-mail Records: The State of the Art; Electronic Risk Management--Reducing Exposure in Litigation; E-Sign & UTEA: How Will They Change the Way You Handle Electronic Records?
E-Sign Here: Prudential Financial is one of the first insurers to enable clients to electronically sign forms and applications.
It would have been pertinent to explain that any such modifications could trigger federal preemption under E-sign.
Though the report indicated that it's still too early to judge whether E-Sign will ultimately help businesses and consumers or lead to an increase in fraud, it states that "it is reasonable to conclude that, thus far, the benefits.