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 ?
In the circumstances, the Keays could have protected themselves by either having one single document detailing the whole of their deal with Morris Homes or by, alternatively, having an entirely separate contract to deal with building works The important lesson to be drawn from this case is that you should be aware that what appears to be an appropriately signed document, purporting to be a contract for the sale of land, will not create a valid contract unless it contains all of the expressly agreed terms.
Rosemont, IL, November 09, 2011 --(PR.com)-- TransNational Bankcard, a merchant processing company, announced today that it will now offer an easier way to handle signed documents.
Ensure the integrity of electronically signed documents so that each record can be authenticated, attributed to the signer, and verified to be a full and accurate representation of the transaction to which it attests, to reflect the intent of the signer, and to be complete and unaltered.
Heinze is considering court action with the Old Trafford outfit having dismissed the legality of the signed document while earlier this week hinting at an illegal approach from the Reds.
Beyond enhanced usability, uSign 4.0 boasts new capabilities for consumer end-users to review and adjust any errors in a signed document before submission and also addresses some of the obstacles to wider acceptance of electronic signature technology.
Data in this format would be editable and would not be considered a signed document. Its status could change to "signed" upon review by the signer and evidence of explicit intention to sign the document, preferably through use of the signer's private key.
The signed document, itself worth around pounds 2,000, relates to the court-martial of a crew member who was to receive a severe reprimand and be docked six months pay ( all for not paying enough attention to the cargo he was put in charge of.
A signed document stating one is aware of the zoning laws and is willing to comply with them may be required before a business license can be obtained.
But before any construction begins Van Patten wants to have a signed document from the Aboriginal community honouring the Ontario legislation tax agreement.
Evidence: A signature authenticates a written document by identifying the signer with the signed document. When the signer makes a mark in a distinctive manner, the writing becomes attributable to the signer.
A signed document isn't enough anymore if it can be proven we knew laws were broken.
Both ministers exchanged the signed document on the extension of strategic cooperation between the two countries up to 2020.