By Francis Kyereh, Information Security Consultant

What is Triple DES?

Triple Data Encryption Standard (Triple DES) is an encryption algorithm which operates in three steps: Encrypt, Decrypt, Encrypt (EDE). The standard works by taking three 56-bit keys (K1, K2 and K3), and encrypting the first with K1, decrypting the next with K2 and encrypting a last time with K3.  Triple DES has two-key and three-key versions. Both two-key and three-key versions of Triple DES can protect data at rest and data in transit, however two-key versions are largely considered insecure now for cardholder data storage.

The PCI Council defines strong cryptography as algorithm based on industry-tested and accepted algorithms, along with key lengths that provide a minimum of 112-bits of effective key strength and proper key-management practices.

Triple DES is widely used in the payment ecosystem as a method for protecting cardholder data at rest. The implementation of Triple DES for protecting stored account data should pass the strong cryptography test of the PCI DSS requirements. Triple DES with double length of the key for cardholder data encryption against PCI requirement 3 is not considered strong cryptography. This article seeks to create awareness that two-key triple DES for encrypting stored cardholder is insecure.

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Why is two-key Triple DES a potential risk to your organisation?

PCI requirement 3.4 requires merchants and service providers to render PAN unreadable anywhere it is stored by using hashing, truncation, tokenisation or strong cryptography. Existing implementations show that two-key triple DES is still prevalent in many cardholder storage protection mechanisms.

The use of triple DES for storage of data is not without risk. Entities should consider the value of the data they are protecting, the duration of protection (as longer protection periods may require stronger algorithms and longer key sizes), and any mitigating controls in place.

Even though two-key triple DES implementation is not recommended for encrypting stored cardholder data, the three-key implementation of 3DES still has use cases that still qualify as strong cryptography.

Why is two-key Triple DES still used?

  • Backward compatibility – Numerous deployed systems support Triple DES Triple DES, and rather than replace those systems, new systems are implemented with compatibility in mind.
  • Lack of understanding – People simply do not understand that Triple DES is no longer secure for most uses.

NIST and PCI Council deprecates two-key Triple DES

The National Institute of Standards and Technology (NIST) proposed the deprecation of certain implementations of triple DES protocol [3]. NIST withdrew support for two-key Triple DES in 2015, and subsequent academic papers have demonstrated that two-key Triple DES provides less than 80 bits of effective key strength even when keys are frequently changed.  NIST provided a guidance that says that double length implementation of Triple DES is no longer considered as secure.

As the PCI SSC definition of strong cryptography includes a minimum of 112-bits of effective key strength, two-key Triple DES which has about 80-bits of effective keys is no longer considered strong cryptography. This therefore means that if your organisation is still using Triple DES, then when conducting an ASV scan it will show up and it will be listed as a fail.

Does your organisation still use two-key Triple DES?

As with all cryptographic algorithms, the lifespan of Triple DES is impacted by the evolution of technologies, vulnerabilities, and threats. Entities using Triple DES to protect stored cardholder data should be aware of risks associated with two-key Triple DES implementation.

There are stronger, cheaper and faster encryption algorithms than triple DES available in the industry. It is strongly advised to ensure that triple DES implementation in the environment is securely configured.

Sysnet can assist through advisory and support on identification of insecure implementations and migration to more secure and acceptable encryption protocols. We have the expertise and the experience to assist your organisation identify and provide solutions in relation to outdated technologies that may leave your business open to being exploited by cyber criminals. For more information, fill out the form below and we’ll be in touch.

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