Hotel key card systems are a critical part of security and convenience in the hospitality industry. In this post, we compare the three encryption algorithms most commonly used in hotel key cards: Crypto1, 3DES (Triple Data Encryption Standard), and AES (Advanced Encryption Standard) — their differences, strengths, and where each fits today.
1. Crypto1: Legacy Security
- Algorithm: Proprietary stream cipher with a 48-bit key.
- Used in: MIFARE Classic 1K cards.
- Strengths: Simple and fast, with low computational requirements; supported by a huge installed base of older locks.
- Weaknesses: Publicly broken since 2008. Cards can be read and cloned with inexpensive tools, and NXP no longer recommends MIFARE Classic for security-relevant applications.
Suitability for hotels: Still widely used in older systems and the right card if your locks are configured for it, but not recommended for new installations. Plan an upgrade path if your property is still on Classic — especially Saflok properties affected by the 2024 “Unsaflok” vulnerability.
2. 3DES: Big Step Up, Being Phased Out Long-Term
- Algorithm: Symmetric block cipher that runs DES three times.
- Key length: MIFARE Ultralight C uses a 112-bit (two-key) 3DES key.
- Used in: ULC (MIFARE Ultralight C) cards — the card many security-upgraded Saflok/dormakaba and Onity systems use — and some older DESFire cards.
- Strengths: Far stronger than Crypto1, with mutual authentication that makes cloning much harder.
- Weaknesses: Slower than AES, and it is an aging standard: NIST disallowed 3DES for new encryption of federal data after 2023, and NXP lists MIFARE Ultralight AES as the replacement for Ultralight C in new designs.
Suitability for hotels: A major security improvement over MIFARE Classic and widely deployed today. If your lock system is configured for ULC, it remains the right card for your property.
3. AES: Current Standard
- Algorithm: Symmetric block cipher standardized by NIST (FIPS 197).
- Key lengths: 128, 192, or 256 bits (hotel key card chips typically use 128-bit).
- Used in: MIFARE Ultralight AES, MIFARE Plus (in AES mode), and MIFARE DESFire EV2/EV3 cards.
- Strengths: No known practical attacks on the algorithm, efficient performance, and long-term support.
- Weaknesses: Requires locks, encoders and software that support the specific AES chip.
Suitability for hotels: The best choice for new and upgraded systems that support it. Lock makers such as VingCard/ASSA ABLOY now support MIFARE Ultralight AES credentials.
Bottom line
The right card is the one your lock system is configured for — but when you have a choice, AES is the strongest, 3DES (ULC) is a solid upgrade over Classic, and Crypto1 (Classic 1K) should be treated as legacy.
Not sure which you have? Contact Hotel & Resort Key Cards — we can identify your card and send a free sample for testing.
Sources & further reading
- Dismantling MIFARE Classic (ESORICS 2008) — Radboud University Nijmegen
- Security Statement on Crypto1 Implementations — NXP / MIFARE
- MIFARE Ultralight C product page — NXP Semiconductors
- SP 800-131A Rev. 2: Transitioning the Use of Cryptographic Algorithms and Key Lengths — NIST
- NIST to Withdraw SP 800-67 Rev. 2 (Triple DES) — NIST
- FIPS 197: Advanced Encryption Standard (AES) — NIST
- Vingcard Boosts Hotel Security with MIFARE Ultralight AES Compatibility — Hospitality Net
- Saflok Lock Vulnerability Can Be Exploited to Open Millions of Doors — SecurityWeek