CRYPTOCELL — Arm TrustZone® CryptoCell 312

Arm® TrustZone® CryptoCell 312 (CRYPTOCELL) is a security subsystem providing root of trust (RoT) and cryptographic services for a device.

Figure 1. CRYPTOCELL block diagram

The following cryptographic features are provided:

True random number generator (TRNG) compliant with NIST 800-90B, AIS-31, and FIPS 140-2
Pseudorandom number generator (PRNG) using underlying AES engine compliant with NIST 800-90A
RSA public key cryptography
- Up to 3072-bit key size
- PKCS#1 v2.1/v1.5
- Optional CRT support
Elliptic curve cryptography (ECC)
- NIST FIPS 186-4 recommended prime field curves using pseudorandom parameters, up to 521 bits:
  - P-192
  - P-224
  - P-256
  - P-384
  - P-521
- SEC 2 recommended prime field curves using pseudorandom parameters, up to 521 bits:
  - secp160r1
  - secp192r1
  - secp224r1
  - secp256r1
  - secp384r1
  - secp521r1
- Koblitz prime field curves using fixed parameters, up to 256 bits:
  - secp160k1
  - secp192k1
  - secp224k1
  - secp256k1
- Edwards/Montgomery curves:
  - Ed25519
  - Curve25519
- ECDH/ECDSA support
Secure remote password protocol (SRP) with up to 3072-bit operations
Hashing functions
- SHA-1
- SHA-2 up to 256 bits
- Keyed-hash message authentication code (HMAC)
AES symmetric encryption
- General purpose AES engine (encrypt/decrypt, sign/verify)
- Supported key size - 128 and 256 bits
- Supported encryption modes: ECB, CBC, CMAC/CBC-MAC, CTR, CCM/CCM*, GCM
ChaCha20/Poly1305 symmetric encryption
- Supported key size - 128 and 256 bits
- Authenticated encryption with associated data (AEAD) mode

Usage

The CRYPTOCELL state is controlled via a register interface. The CRYPTOCELL cryptographic functions are accessible through a software library provided in the device SDK.

To enable CRYPTOCELL, use register ENABLE.

Note: To prevent the device from reaching the System ON All Idle state, enable the CRYPTOCELL subsystem.

Direct memory access (DMA)

CRYPTOCELL features direct access memory (DMA) to allow cryptographic operations on memory mapped regions without involving the CPU.

The maximum DMA transaction size is limited to 2¹⁶-1 bytes. See Memory for information about memory that is accessible through the CRYPTOCELL DMA.

The CRYPTOCELL DMA can configure the security setting used for bus transactions.

Any data stored in a memory type not accessible by the CRYPTOCELL DMA engine must be copied to a memory type accessible by the direct memory before it can be processed by the CRYPTOCELL subsystem.

Standards

Arm TrustZone® CryptoCell 312 (CRYPTOCELL) is compliant with the protocol specifications and standards shown in the following table.

Table 1. CRYPTOCELL cryptography standards
Algorithm family	Identification code	Document title
TRNG	NIST SP 800-90B	Recommendation for the Entropy Sources Used for Random Bit Generation
	AIS-31	A proposal for: Functionality classes and evaluation methodology for physical random number generators
	FIPS 140-2	Security Requirements for Cryptographic Modules
PRNG	NIST SP 800-90A	Recommendation for Random Number Generation Using Deterministic Random Bit Generators
Stream cipher	Chacha	ChaCha, a variant of Salsa20, Daniel J. Bernstein, January 28th 2008
MAC	Poly1305	The Poly1305-AES message-authentication code, Daniel J. Bernstein Cryptography in NaCl, Daniel J. Bernstein
Key agreement	SRP	The Secure Remote Password Protocol, Thomas Wu, November 11th 1997
Key derivation	NIST SP 800-108	Recommendation for Key Derivation Using Pseudorandom Functions. Compliant with section 5.1
AES	FIPS-197	Advanced Encryption Standard (AES). Compliant with 128-bit and 256-bit key size only
	NIST SP 800-38A	Recommendation for Block Cipher Modes of Operation - Methods and Techniques. Compliant with sections 6.1, 6.2, 6.4, and 6.5.
	NIST SP 800-38B	Recommendation for Block Cipher Modes of Operation: The CMAC Mode for Authentication
	NIST SP 800-38C	Recommendation for Block Cipher Modes of Operation: The CCM Mode for Authentication and Confidentiality
	ISO/IEC 9797-1	AES CBC-MAC per ISO/IEC 9797-1 MAC algorithm 1
	IEEE 802.15.4-2011	IEEE Standard for Local and metropolitan area networks - Part 15.4: Low-Rate Wireless Personal Area Networks (LR-WPANs), Annex B.4: Specification of generic CCM* mode of operation
Hash	FIPS 180-3	Secure Hash Standard (SHA1, SHA-224, SHA-256)
Hash	RFC2104	HMAC: Keyed-Hashing for Message Authentication
RSA	PKCS#1	Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications v1.5/2.1
Diffie-Hellman	ANSI X9.42	Public Key Cryptography for the Financial Services Industry: Agreement of Symmetric Keys Using Discrete Logarithm Cryptography
Diffie-Hellman	PKCS#3	Diffie-Hellman Key-Agreement Standard
ECC	ANSI X9.63	Public Key Cryptography for the Financial Services Industry - Key Agreement and Key Transport Using Elliptic Curve Cryptography
	IEEE 1363	Standard Specifications for Public-Key Cryptography
	ANSI X9.62	Public Key Cryptography For The Financial Services Industry: The Elliptic Curve Digital Signature Algorithm (ECDSA)
	Ed25519	Edwards-curve, Ed25519: high-speed high-security signatures, Daniel J. Bernstein, Niels Duif, Tanja Lange, Peter Schwabe, and Bo-Yin Yang
	Curve25519	Montgomery curve, Curve25519: new Diffie-Hellman speed records, Daniel J. Bernstein
	FIPS 186-4	Digital Signature Standard (DSS). Compliant with sections 5.1, 6.2, 6.3, 6.4, B.1.2, B.2.2, B.3.6, B.4.2, C.3.1, C.3.3, C.3.5, C.9, and D.1.2.
	SEC 2	Recommended Elliptic Curve Domain Parameters, Certicom Research
	NIST SP 800-56A rev. 2	Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography

Registers

Table 2. Instances
Base address	Domain	Peripheral	Instance	Secure mapping	DMA security	Description	Configuration
0x50844000	APPLICATION	CRYPTOCELL	CRYPTOCELL	S	NSA	CryptoCell subsystem control interface

Table 3. Register overview
Register	Offset	Security	Description
ENABLE	0x500		Enable CRYPTOCELL subsystem.

ENABLE

Address offset: 0x500

Enable CRYPTOCELL subsystem.

Bit number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
ID																																			A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
ID	R/W	Field	Value ID	Value								Description
A	RW	ENABLE										Enable or disable the CRYPTOCELL subsystem.
			Disabled	0								CRYPTOCELL subsystem disabled.
			Enabled	1								CRYPTOCELL subsystem enabled. When enabled, the CRYPTOCELL subsystem can be initialized and controlled through the CryptoCell firmware API.