Firma electrónica y firma digital no son lo mismo

The terms "electronic signature" and "digital signature" are often used interchangeably, but they are not the same thing. The confusion persists until a dispute arises over who signed a document and evidence is needed to prove otherwise. This difference is no longer just a matter of terminology; it determines whether a document is valid.

Two different levels of signature There are two distinct categories of signatures: electronic and digital. An electronic signature is a broad concept that includes any electronic data a person uses with the intention of signing, such as a typed name in an email, an "accept" box, a scanned image of a handwritten signature, or a digital pen stroke on a tablet.

It is a legal category and a functional one that indicates the intention to sign, not how the signature is verified. Digital signatures are much more specific: they are cryptographic techniques applied to a document using public key cryptography. They are not just a type of drawing or a button; they are mathematical keys used for verification.

Relationship between electronic and digital signatures Digital signatures are a subset of electronic signatures. While every digital signature is electronic, not every electronic signature is digital. The digital signature provides technical guarantees that can be verified, while an electronic signature does not. How digital signatures work The signer has a pair of keys: a private key, which is kept secret and never shared, and a public key, which can be freely distributed.

The process works as follows: The document's hash (a unique digital fingerprint) is calculated. The hash is signed with the private key. The resulting signature is then attached to the document. Verification is simple: anyone can use the public key to confirm that the signature was created by the corresponding private key and that the hash matches the current document.

Two guarantees emerge: integrity (if a single byte is changed, the hash changes and the signature no longer matches) and origin (only the person with the private key could have created the signature). Combined, these guarantee non-repudiation, making it difficult for the signer to deny having signed. Proof of each signature type A simple electronic signature, such as a typed name or an image, shows intention, but it does not prove integrity or origin.

It is a valid signature, but weak when challenged. A digital signature, on the other hand, is broken if the document is altered, and it ties the act to a specific key. This is the practical difference: it's not that one is "valid" and the other is not—many jurisdictions recognize the effects of an electronic signature generally and reserve enhanced effects for a signature that meets certain technical requirements—but they prove different things.

The link to trust The key distinction almost everyone overlooks is that a digital signature proves that the document corresponds to a private key. Whether that key belongs to a person or an impostor is a separate trust issue. This is resolved through a Public Key Infrastructure (PKI): a certificate issued by an authority that verified the identity, or the process by which you verified the signer.

The mathematics links the document to the key; trust links the key to the person. Without the latter, a perfect digital signature could belong to anyone. Choosing the right signature The choice depends on the document's purpose. For low-risk internal approvals, a simple electronic signature is sufficient and there's no need for the additional friction of a digital signature.

When the document may be contested by a third party—such as a high-value contract, evidence, or a critical authorization—a digitally signed document with a well-established trust infrastructure provides verifiable proof instead of relying on verbal assurances. Practical rule of thumb: choose the level of proof based on the level of dispute you anticipate, not out of habit.