SCP03

SCP03

Secure Channel Protocol 03 (AES-based secure channel protocol." data-category="Software">SCP03) is the current-generation secure communication protocol defined by GlobalPlatform for authenticated and encrypted management operations between a host application and a smart card. Replacing the legacy 3DES-based SCP02, SCP03 uses AES for both encryption and integrity protection, providing a modern cryptographic foundation for applet installation, key management, and card lifecycle operations.

Protocol Flow

An SCP03 session is established through a three-step mutual authentication handshake:

1. INITIALIZE UPDATE: The host sends a random challenge. The card responds with its own challenge, a key diversification value, and a card cryptogram (AES-CMAC over both challenges using the session MAC key).
2. EXTERNAL AUTHENTICATE: The host verifies the card cryptogram, derives session keys, and sends a host cryptogram. The card verifies the host cryptogram to complete mutual authentication.
3. Secure Session: All subsequent APDUs are wrapped with AES-CMAC integrity and optionally AES-CBC encryption.

Session Key Derivation

SCP03 derives three session keys from static card keys using the AES-based KDF specified in NIST SP 800-108:

The derivation uses the host challenge, card challenge, and a key derivation constant, ensuring unique session keys for every authenticated session. Static card keys are never used directly for data protection.

Security Levels

SCP03 supports three security levels, selectable per session:

Most production deployments use full bidirectional protection (C-MAC + C-DECRYPTION + R-MAC) for applet loading and key rotation operations, as both the command data (applet code, new keys) and response data (status, confirmations) are security-sensitive.

SCP03 vs SCP02

SCP03 is mandatory for new GlobalPlatform deployments. The migration from SCP02 is particularly important for SIM cards and eSIM platforms where GSMA SAS certification increasingly requires AES-based secure channels.