What an encryption algorithm is
An encryption algorithm is a defined set of mathematical rules for transforming readable data, called plaintext, into ciphertext. The algorithm works with an encryption key. Decryption uses the appropriate key to turn ciphertext back into readable data.
The algorithm is the method; encryption is the process that uses it. For example, AES is an encryption algorithm, while encrypting a card number before sending it is an encryption operation. The algorithm does not need to be secret. The encryption key must be protected.
An encryption algorithm is only part of the protection; the keys and systems around it matter too.
How algorithms and keys work
AES is a widely used symmetric encryption algorithm. It processes data in 128-bit blocks and supports 128-, 192-, and 256-bit keys. Symmetric encryption uses the same secret key to encrypt and decrypt data, so access to that key affects who can read the original information.
Public-key, or asymmetric, cryptography uses related public and private keys for different operations. RSA is one example. In either approach, the algorithm, key strength, and protection of the keys all matter. A sound algorithm cannot protect data if an unauthorized person gets the key.
Why it matters when you accept payments
Encryption helps keep payment data unreadable to people who intercept it while it is transmitted or stored. In a PCI-approved Point-to-Point Encryption (P2PE) solution, an approved point-of-interaction device encrypts account data before it leaves the device. The PCI P2PE glossary describes merchant environments for physical and mail-order or telephone-order payments, not e-commerce.
Encryption is one security control, not proof that your business meets every PCI DSS requirement. Your exposure also depends on which systems handle readable card data and how encryption keys are generated, stored, accessed, used, and destroyed. Encryption algorithms do not set your interchange rate or create a standard card-processing fee.
What you can actually change
You may not manage the payment system's cryptography directly, but you can verify where payment data is encrypted and who can access its keys. Those details affect whether stolen data or a compromised system exposes readable card information.
- Identify which checkout, storage, and transmission systems handle readable card data.
- Confirm which encryption algorithm protects that data and whether it is an industry-tested, accepted choice.
- Limit key access to authorized roles and review how keys are stored, rotated, and removed.
- For in-person payments, verify whether your solution uses PCI-approved P2PE devices and processes.
- Map payment data. List the systems that receive, transmit, or store readable card details, then identify where each system encrypts them.
- Review key access. Find out which roles can use or manage encryption keys and how access changes when staff responsibilities change.
- Verify device protections. For in-person transactions, confirm that your payment devices and process are part of a PCI-approved P2PE solution.
Frequently asked questions
What is an encryption algorithm in payment processing?
It is a set of mathematical rules used to transform readable payment data into ciphertext with an encryption key. The data becomes readable again through decryption with the appropriate key. AES is one example of an encryption algorithm.
Is an encryption algorithm the same as encryption?
No. The algorithm is the method, and encryption is the process that applies that method to data using a key. For example, AES is an algorithm; using AES to protect a card number is encryption.
Does encryption alone make my business PCI compliant?
No. Encryption is a security control, but PCI DSS compliance involves other requirements and depends on which systems handle card data. Key management also matters, because someone with unauthorized access to a key could expose encrypted information.