digital signature


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Related to digital signature: Digital certificate, Digital Signature Algorithm

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 ?
Go back to Email Security -> under Encrypted E-mail, check the Add digital signature to outgoing messages and then Send clear text signed messages when sending signed messages.
THE Central Board of Direct Taxes ( CBDT) has developed a new easy- to- use software as taxpayers have been complaining about problems in filing their income tax returns with digital signatures.
According to DocuSign, the acquisition builds on a three year business partnership between DocuSign and ARX, bringing together ARX's CoSign digital signature technology with DocuSign's Digital Transaction Management platform.
Thus any Word, Excel, PowerPoint or PDF documents that use the Windows Trust Services can directly use the ID Card to generate the digital signatures using the PKI [public-key infrastructure] certificates available in the ID Card.
While it might seem that this could be accomplished by creating a fill-in PDF form, that would not meet the requirements of a "digital signature" if the data required to be retained are not captured and stored for each electronic signature.
Until now, it was not possible to use a secret key which contained errors in digital signatures, and therefore biometric information has not been used.
Biometrics, despite its potential utility as a form of electronic signature, has at least two drawbacks in comparison with the digital signature: (1) The attachment of a person's biological traits to a document does not ensure that the document has not been altered, i.e., it "does not freeze the contents of the document;" [45] and (2) The recipient of the document must have a database of biological traits of all signatories dealt with in order to verify that a particular person sent the document.
The concept of a "hash" function needs to be described, as this process is used natively in ELN products and in combination with the digital signature process.
The new website www.isnsc.ae provides Secure Socket Layer (SSL) services, digital certificates that can be used for email security, a collection of digital signature solutions and also security assessment and various consulting services, said a company statement.
Before document signers establish their digital signature, they are presented with a set of multiple choice questions that only the true signee can answer.
In the framework of the cross-border digital signature solution in the company registration portal, one European state will acknowledge for the first time the digital signature of a citizen of another European state.
In the next section we introduce some background notions about the signature generation process and we give the motivations of our work, by introducing the vulnerability of digital signature which we deal with.

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