Encryption and digital signing are two different cryptographic operations. Encryption protects confidentiality: it scrambles data so only the intended recipient can read it. Signing protects authenticity and integrity: it proves who sent the data and that it was not altered, and provides non-repudiation. Encryption keeps data secret; signing proves who sent it. They are often used together.
Encryption and signing solve different problems. Encryption keeps data confidential, scrambling it so only the intended recipient can read it. Digital signing does not hide data; it proves the data’s authenticity and integrity, confirming who sent it and that it was not changed, and provides non-repudiation. In short, encryption protects secrecy, signing proves origin, and together they cover all the main goals of cryptography.
Key Takeaways
- Encryption provides confidentiality; digital signing provides authenticity, integrity, and non-repudiation.
- For confidentiality, you encrypt with the recipient’s public key, and only they can decrypt with their private key.
- For signing, you hash the message and transform that hash with your private key; anyone can verify it with your public key.
- Signing does not keep data secret, and encryption alone does not prove who sent the data. That is why they are often used together.
- Together, encryption and signing meet all four goals of cryptography: Confidentiality, Integrity, Authenticity, and Non-repudiation.
What Is Encryption?
Encryption converts readable plaintext into scrambled ciphertext using an algorithm and a key, so that anyone without the key sees only unreadable data. Its purpose is confidentiality: keeping data secret from everyone except the intended recipient. Encryption comes in two forms. Symmetric encryption uses one shared key for both encryption and decryption (fast, used for bulk data). Asymmetric encryption uses a public/private key pair. For confidentiality with asymmetric encryption, the correct approach is to encrypt with the recipient’s public key, because then only the holder of the matching private key, the intended recipient, can decrypt and read the data.
What Is Digital Signing?
Digital signing does the opposite job from encryption: instead of hiding data, it proves who created it and that it has not been altered. It does not necessarily keep the data secret. Signing uses the sender’s own key pair, and it works like this:
- Hash the message: The sender runs the message through a hash function (such as SHA-256) to produce a fixed-size digest, a fingerprint of the message.
- Sign with the private key: The sender transforms that hash with their private key to produce the digital signature, which is sent along with the message.
- Verify with the public key: The recipient independently hashes the received message, and uses the sender’s public key to check the signature. If the signature is valid and the two hashes match, the message is authentic and unaltered.
Because only the sender holds their private key, a valid signature proves the message came from them (authenticity) and that no one changed it in transit (integrity). It also provides non-repudiation: the sender cannot later deny signing it. Note the key usage is the reverse of encryption, you sign with your own private key, whereas you encrypt with the recipient’s public key.
Encryption vs Signing: Side-by-Side Comparison
The two operations are easy to confuse because both use keys and cryptographic algorithms, but their goals and key usage are opposite:
| Aspect | Encryption | Digital Signing |
|---|---|---|
| Main goal | Confidentiality (keep data secret) | Authenticity, integrity, non-repudiation |
| What it protects | The contents of the data | The origin and integrity of the data |
| Does it hide data? | Yes, data becomes unreadable | No, the data stays readable |
| Key used (asymmetric) | Encrypt with the recipient’s public key | Sign with the sender’s private key |
| Who reverses it | Recipient decrypts with their private key | Anyone verifies with the sender’s public key |
| Uses hashing? | No | Yes, the message is hashed, then the hash is signed |
| Answers the question | Can anyone else read this? | Who sent this, and was it changed? |
Why Use Digital Signatures?
Digital signatures matter because encryption alone cannot tell you who sent a message or whether it was tampered with. Signatures add exactly that assurance, and they are the reason to sign:
AUTHENTICITY: a valid signature proves the message or document genuinely came from the claimed sender, because only they hold the private key.
INTEGRITY: if even one bit of the signed data changes, the signature no longer verifies, so any tampering is immediately detected.
NON-REPUDIATION: because the signature could only be produced with the sender’s private key, the sender cannot later deny having sent or approved the data, which is essential for contracts, legal documents, and financial transactions.
TRUST AND COMPLIANCE: signatures underpin software code signing, secure email, digital certificates, and many regulatory requirements, letting recipients trust data without a prior relationship.
Using Encryption and Signing Together
Because encryption and signing protect different things, sensitive communications often use both. When you both encrypt and sign a message, you achieve all four goals of cryptography at once: Confidentiality and integrity from encryption (only the recipient can read it), and authenticity and non-repudiation from the signature (the recipient knows who sent it and that it is unchanged). This combination is what secure email standards (such as S/MIME and PGP), TLS, and signed-and-encrypted documents rely on, and it is often required to meet standards like FIPS and GDPR. As a rule of thumb: sign with your own private key, encrypt with the recipient’s public key.
Common Encryption and Signing Algorithms
Different algorithms are used for each job (some algorithms, like RSA, can do both):
- Symmetric encryption: AES is the modern standard. Older ones like DES, RC4, and (to a lesser extent) Blowfish and Twofish appear too, though DES and RC4 are broken and should not be used.
- Asymmetric encryption/key exchange: RSA, Elliptic Curve Cryptography (ECC), and Diffie-Hellman (for key exchange). RSA and ECC handle both encryption and signing.
- Digital signatures: RSA, ECDSA, and EdDSA are the common modern signature algorithms. DSA is older and now rarely used. The post-quantum signature standards ML-DSA and SLH-DSA are emerging replacements.
How Encryption Consulting Helps
Using encryption and signing correctly, with the right algorithms, correct key usage, and sound key management, is central to a strong security posture. Encryption Consulting’s Encryption Advisory Services assess how encryption and digital signatures are used across your environment, correct misconfigurations, and design compliant implementations aligned to standards like NIST, FIPS, and GDPR. For digital signing specifically, our CodeSign Secure platform secures signing keys and automates code signing across your pipelines, with certificate management, timestamping, and audit trails. Backed by ISO/IEC 27001:2022 and SOC 2 certified practices.
Frequently Asked Questions
What is the difference between encryption and signing?
Encryption and signing are different cryptographic operations. Encryption protects confidentiality: it scrambles data into unreadable ciphertext so only the intended recipient can read it. Digital signing protects authenticity and integrity: it does not hide the data, but proves who sent it and that it was not altered, and provides non-repudiation. The key usage is opposite too: you encrypt with the recipient’s public key, but you sign with your own private key. They are often used together to cover all goals.
Why should you use digital signatures?
Digital signatures matter because encryption alone cannot tell you who sent a message or whether it was tampered with. A digital signature proves authenticity (it genuinely came from the claimed sender, who alone holds the private key), integrity (any change breaks the signature), and non-repudiation (the sender cannot later deny signing it). This is essential for contracts, legal and financial transactions, secure email, software code signing, and digital certificates, where recipients must trust the origin and integrity of data.
How does digital signing work?
To sign, the sender hashes the message with a hash function like SHA-256 to create a fixed-size digest, then transforms that hash with their private key to produce the signature, which travels with the message. To verify, the recipient independently hashes the received message and uses the sender’s public key to check the signature. If the signature is valid and the two hashes match, the message is authentic and unaltered. Only the sender’s private key could have produced a valid signature.
Which key is used for encryption versus signing?
The key usage is opposite for the two operations. For confidentiality encryption with an asymmetric key pair, you encrypt with the recipient’s public key, and only they can decrypt with their private key. For signing, you sign with your own private key, and anyone can verify the signature with your public key. A simple way to remember it: encrypt with the recipient’s public key, sign with your own private key.
Does a digital signature encrypt the data?
No. A digital signature does not encrypt or hide the data, the signed data remains readable. Signing only proves who created the data and that it has not been altered. If you also need to keep the data secret, you must encrypt it as well. That is why sensitive messages are often both signed and encrypted: the signature provides authenticity, integrity, and non-repudiation, while the encryption provides confidentiality. The two operations are complementary, not interchangeable.
Can you use encryption and signing together?
Yes, and for sensitive communications it is common practice. Signing with your private key and encrypting with the recipient’s public key together achieve all four goals of cryptography: confidentiality and integrity from the encryption, and authenticity and non-repudiation from the signature. Secure email standards like S/MIME and PGP, TLS, and signed-and-encrypted documents all rely on this combination, which is often required to meet compliance standards such as FIPS and GDPR.
Get Encryption and Signing Right
Correct key usage and strong key management make the difference between real security and a false sense of it. Explore Encryption Consulting’s Encryption Advisory Services and CodeSign Secure to implement encryption and digital signatures correctly across your organization.