What Is a Digital Signature? Digital vs Electronic Signature

An electronic signature is the broad legal category: any sound, symbol or process a person adopts with intent to sign. A digital signature is one technical way to make one, using certificates and cryptography. Every digital signature is electronic; most electronic signatures are not digital signatures.

What is a digital signature?

A digital signature is the output of a cryptographic operation on a document that lets anyone check who signed it and whether it changed afterwards. NIST, the US standards body, defines it in FIPS 186-5 as "the result of a cryptographic transformation of data that, when properly implemented, provides a mechanism for verifying origin authentication, data integrity, and signatory non-repudiation."

In plain terms, a digital signature proves three things:

• Origin: the signature was made with the signer's private key, which only the signer should hold.
• Integrity: the document has not changed since it was signed.
• Non-repudiation support: the signer cannot easily claim someone else made the signature.

It does not hide the document. NIST SP 800-63-4, on the same glossary page, says digital signatures provide authenticity, integrity and non-repudiation support "but not confidentiality or replay attack protection." Anyone who has the file can still read it.

How a digital signature works

A digital signature takes four steps, and your signing software does all of them for you:

1. Hash the document. The software computes a short, fixed-length fingerprint (a hash) of the file. Change one character and the hash changes.
2. Sign the hash with the private key. The signer's private key transforms the hash. The result is the signature, and it is bound to that exact version of the file.
3. Attach the certificate. A digital certificate travels with the signature and ties the signer's public key to their identity. Adobe describes each digital ID as "issued by a trusted third party, such as a bank or government, after thoroughly verifying your identity" (Adobe, checked September 2026).
4. Verify with the public key. The reader's software uses the public key from the certificate to check the signature against a fresh hash of the file. If they match, the file is unchanged since signing.

If you want the maths behind the private and public keys, Computerphile's explainer walks through the same idea step by step.

What are Digital Signatures? - Computerphile

What is an electronic signature?

An electronic signature is any electronic sound, symbol or process that a person attaches to a record with the intent to sign it. That is the US legal definition.

The ESIGN Act, 15 U.S.C. 7006(5), defines it 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."

The definition is about intent, not technology. All of these are electronic signatures:

• A typed name at the bottom of an agreement.
• A signature drawn with a finger or mouse on a screen.
• A click on an "I agree" or "Sign" button.
• A scanned image of your handwritten signature placed in a file.
• A certificate-based digital signature, which is an electronic signature too.

If you want to make a drawn or typed signature, our guide to signing your name electronically covers each method.

Digital signature vs electronic signature: the differences

The short version: an electronic signature is defined by the law and the signer's intent, and a digital signature is defined by the cryptography underneath it.

The legal row is where most pages overstate things. The ESIGN Act, 15 U.S.C. 7001(a)(1), says a signature, contract or other record "may not be denied legal effect, validity, or enforceability solely because it is in electronic form." It does not say a signature needs a certificate.

What a certificate adds is technical evidence. What a standard e-signature relies on instead is its audit trail: the record of who was sent the document, how they were verified, and when they signed.

Which one do you need?

For most everyday US business agreements, such as NDAs, client contracts and offer letters, a standard e-signature with a good audit trail is what gets used. Certificate-based digital signatures are typically asked for when a counterparty, agency or regulator specifically requires them. Check the requirement before you send.

The tree in words:

• Someone asked for a certificate-based signature: use one. The requirement decides it, not your preference.
• Nobody asked, and it is an everyday agreement: a standard e-signature with an audit trail is the usual choice. Our guide to e-signing an NDA and our walkthrough of how to electronically sign a PDF show the steps.
• Nobody asked, but the document is unusual or regulated: check the signing requirement for that document before you send it.

If you are the sender and need to place a signature field for someone else, see how to add a signature block to a PDF for someone else to sign.

Sign vs signature: the difference

"Sign" is the verb: the act of putting your name or mark on something. "Signature" is the noun: the name or mark you leave. Wiktionary defines a signature as "a person's name, written by that person, used as identification or to signify approval."

To sign is "to write one's signature on (something)." Online the split holds: you e-sign a document, and what you leave is an electronic signature.

Where SignWith fits

SignWith makes electronic signatures, not certificate-based digital signatures. It is built for the everyday agreements in the tree above, and the proof of who signed lives in the audit trail:

• Signers verify their identity with a one-time passcode sent to their email.
• Every completed document comes with a Certificate of Completion that records timestamps, IP addresses, device and browser details and email events, sealed with a SHA-256 hash.
• Completed copies are emailed to all parties.

In the US, SignWith's email OTP verification, consent record, signing record and audit trail are designed to support the requirements of the ESIGN Act and UETA.

There is no subscription: you buy credits, and a credit is used only when a document is signed. 1 credit = 1 signed document, however many people sign it, and every account gets 3 signed documents free each month. To make a signature image first, try the free e-signature tool.

Who should use which:

• Use SignWith if you want a simple way to get a document signed, with no subscription and no hidden fees.
• Pick another tool if you need a certificate-based digital signature, a team setup, B2B workflows, a formal compliance program or advanced features. Team accounts, templates, bulk send, reminders and integrations are coming soon on SignWith, not live today; the SignWith API is.
• For certificate-based signing, Adobe Acrobat is the obvious alternative. Adobe's digital signatures page says you can choose from hundreds of certificate authorities and trust service providers on its Approved Trust List (checked September 2026).
• The Adobe catch is the subscription: Acrobat Standard is listed at $14.99 a month on an annual plan, and Adobe charges up to half your remaining annual commitment if you cancel after 14 days (Adobe Acrobat plans, checked September 2026). Check which plan includes the certificate features you need.

E-signature rules vary by country, state and document type, so check with a legal professional that an e-signature suits your specific agreement before you rely on it.