Basic Concepts of Local Key Management

Familiarity with the following concepts is helpful because they are used throughout your development process.

TEE

Trusted Execution Environment (TEE) is a secure area of a main processor of a smartphone, tablet, or a mobile device. Any data in the TEE cannot be read or tampered with by any code outside it. The TEE provides a secure execution environment for trusted applications (TAs) to ensure end-to-end security by features, such as isolated execution, integrity of applications, confidentiality of their assets, and data access permissions.

Key Material Format

HUKS defines a set of key material formats for key pairs, public keys, and private keys of different cryptographic algorithms. The key material formats are used when a key is imported or exported.

Key Pair Material Format

Key pair material = Key pair material header + Key pair material content

For example, an application needs an RSA key in Uint8Array format, the variables are assigned with values based on the structure of the RSA key pair material in the memory.

The following figure illustrates the structure of the RSA key material. For details about the key material formats of other algorithms, see the tables below.

keyt

The key algorithm is a value of HuksKeyAlg.

let rsa2048KeyPairMaterial = new Uint8Array([
    0x01, 0x00, 0x00, 0x00, // Key algorithm: huks.HuksKeyAlg.HUKS_ALG_RSA = 1
    0x00, 0x08, 0x00, 0x00, // Key size (bit): 2048
    0x00, 0x01, 0x00, 0x00, // Length of modulus n (byte): 256
    0x03, 0x00, 0x00, 0x00, // Length of the public key exponent e (byte): 3
    0x00, 0x01, 0x00, 0x00, // Length of the private key exponent d (byte): 256
    // Modulus n
    0xc5, 0x35, 0x62, 0x48, 0xc4, 0x92, 0x87, 0x73, 0x0d, 0x42, 0x96, 0xfc, 0x7b, 0x11, 0x05, 0x06,
    0x0f, 0x8d, 0x66, 0xc1, 0x0e, 0xad, 0x37, 0x44, 0x92, 0x95, 0x2f, 0x6a, 0x55, 0xba, 0xec, 0x1d,
    0x54, 0x62, 0x0a, 0x4b, 0xd3, 0xc7, 0x05, 0xe4, 0x07, 0x40, 0xd9, 0xb7, 0xc2, 0x12, 0xcb, 0x9a,
    0x90, 0xad, 0xe3, 0x24, 0xe8, 0x5e, 0xa6, 0xf8, 0xd0, 0x6e, 0xbc, 0xd1, 0x69, 0x7f, 0x6b, 0xe4,
    0x2b, 0x4e, 0x1a, 0x65, 0xbb, 0x73, 0x88, 0x6b, 0x7c, 0xaf, 0x7e, 0xd0, 0x47, 0x26, 0xeb, 0xa5,
    0xbe, 0xd6, 0xe8, 0xee, 0x9c, 0xa5, 0x66, 0xa5, 0xc9, 0xd3, 0x25, 0x13, 0xc4, 0x0e, 0x6c, 0xab,
    0x50, 0xb6, 0x50, 0xc9, 0xce, 0x8f, 0x0a, 0x0b, 0xc6, 0x28, 0x69, 0xe9, 0x83, 0x69, 0xde, 0x42,
    0x56, 0x79, 0x7f, 0xde, 0x86, 0x24, 0xca, 0xfc, 0xaa, 0xc0, 0xf3, 0xf3, 0x7f, 0x92, 0x8e, 0x8a,
    0x12, 0x52, 0xfe, 0x50, 0xb1, 0x5e, 0x8c, 0x01, 0xce, 0xfc, 0x7e, 0xf2, 0x4f, 0x5f, 0x03, 0xfe,
    0xa7, 0xcd, 0xa1, 0xfc, 0x94, 0x52, 0x00, 0x8b, 0x9b, 0x7f, 0x09, 0xab, 0xa8, 0xa4, 0xf5, 0xb4,
    0xa5, 0xaa, 0xfc, 0x72, 0xeb, 0x17, 0x40, 0xa9, 0xee, 0xbe, 0x8f, 0xc2, 0xd1, 0x80, 0xc2, 0x0d,
    0x44, 0xa9, 0x59, 0x44, 0x59, 0x81, 0x3b, 0x5d, 0x4a, 0xde, 0xfb, 0xae, 0x24, 0xfc, 0xa3, 0xd9,
    0xbc, 0x57, 0x55, 0xc2, 0x26, 0xbc, 0x19, 0xa7, 0x9a, 0xc5, 0x59, 0xa3, 0xee, 0x5a, 0xef, 0x41,
    0x80, 0x7d, 0xf8, 0x5e, 0xc1, 0x1d, 0x32, 0x38, 0x41, 0x5b, 0xb6, 0x92, 0xb8, 0xb7, 0x03, 0x0d,
    0x3e, 0x59, 0x0f, 0x1c, 0xb3, 0xe1, 0x2a, 0x95, 0x1a, 0x3b, 0x50, 0x4f, 0xc4, 0x1d, 0xcf, 0x73,
    0x7c, 0x14, 0xca, 0xe3, 0x0b, 0xa7, 0xc7, 0x1a, 0x41, 0x4a, 0xee, 0xbe, 0x1f, 0x43, 0xdd, 0xf9,
    // Public key exponent e
    0x01, 0x00, 0x01,
    // Private key exponent d
    0x88, 0x4b, 0x82, 0xe7, 0xe3, 0xe3, 0x99, 0x75, 0x6c, 0x9e, 0xaf, 0x17, 0x44, 0x3e, 0xd9, 0x07,
    0xfd, 0x4b, 0xae, 0xce, 0x92, 0xc4, 0x28, 0x44, 0x5e, 0x42, 0x79, 0x08, 0xb6, 0xc3, 0x7f, 0x58,
    0x2d, 0xef, 0xac, 0x4a, 0x07, 0xcd, 0xaf, 0x46, 0x8f, 0xb4, 0xc4, 0x43, 0xf9, 0xff, 0x5f, 0x74,
    0x2d, 0xb5, 0xe0, 0x1c, 0xab, 0xf4, 0x6e, 0xd5, 0xdb, 0xc8, 0x0c, 0xfb, 0x76, 0x3c, 0x38, 0x66,
    0xf3, 0x7f, 0x01, 0x43, 0x7a, 0x30, 0x39, 0x02, 0x80, 0xa4, 0x11, 0xb3, 0x04, 0xd9, 0xe3, 0x57,
    0x23, 0xf4, 0x07, 0xfc, 0x91, 0x8a, 0xc6, 0xcc, 0xa2, 0x16, 0x29, 0xb3, 0xe5, 0x76, 0x4a, 0xa8,
    0x84, 0x19, 0xdc, 0xef, 0xfc, 0xb0, 0x63, 0x33, 0x0b, 0xfa, 0xf6, 0x68, 0x0b, 0x08, 0xea, 0x31,
    0x52, 0xee, 0x99, 0xef, 0x43, 0x2a, 0xbe, 0x97, 0xad, 0xb3, 0xb9, 0x66, 0x7a, 0xae, 0xe1, 0x8f,
    0x57, 0x86, 0xe5, 0xfe, 0x14, 0x3c, 0x81, 0xd0, 0x64, 0xf8, 0x86, 0x1a, 0x0b, 0x40, 0x58, 0xc9,
    0x33, 0x49, 0xb8, 0x99, 0xc6, 0x2e, 0x94, 0x70, 0xee, 0x09, 0x88, 0xe1, 0x5c, 0x4e, 0x6c, 0x22,
    0x72, 0xa7, 0x2a, 0x21, 0xdd, 0xd7, 0x1d, 0xfc, 0x63, 0x15, 0x0b, 0xde, 0x06, 0x9c, 0xf3, 0x28,
    0xf3, 0xac, 0x4a, 0xa8, 0xb5, 0x50, 0xca, 0x9b, 0xcc, 0x0a, 0x04, 0xfe, 0x3f, 0x98, 0x68, 0x81,
    0xac, 0x24, 0x53, 0xea, 0x1f, 0x1c, 0x6e, 0x5e, 0xca, 0xe8, 0x31, 0x0d, 0x08, 0x12, 0xf3, 0x26,
    0xf8, 0x5e, 0xeb, 0x10, 0x27, 0xae, 0xaa, 0xc3, 0xad, 0x6c, 0xc1, 0x89, 0xdb, 0x7d, 0x5a, 0x12,
    0x55, 0xad, 0x11, 0x19, 0xa1, 0xa9, 0x8f, 0x0b, 0x6d, 0x78, 0x8d, 0x1c, 0xdf, 0xe5, 0x63, 0x82,
    0x0b, 0x7d, 0x23, 0x04, 0xb4, 0x75, 0x8c, 0xed, 0x77, 0xfc, 0x1a, 0x85, 0x29, 0x11, 0xe0, 0x61,
]);

RSA key pair material format

Key
Algorithm Key
Size Modulus n
Length L_n Public Key Exponent e
Length L_e Private Key Exponent d
Length L_d n e d

4 bytes 4 bytes 4 bytes 4 bytes 4 bytes L_n bytes L_e bytes L_d bytes
ECC key pair material format

Key
Algorithm Key
Size X Coordinate
Length L_x Y Coordinate
Length L_y Z Coordinate
Length L_z x y z

4 bytes 4 bytes 4 bytes 4 bytes 4 bytes L_x bytes L_y bytes L_z bytes

Key Algorithm	Key Size	Modulus n Length L_n	Public Key Exponent e Length L_e	Private Key Exponent d Length L_d	n	e	d
4 bytes	4 bytes	4 bytes	4 bytes	4 bytes	L_n bytes	L_e bytes	L_d bytes

Key Algorithm	Key Size	X Coordinate Length L_x	Y Coordinate Length L_y	Z Coordinate Length L_z	x	y	z
4 bytes	4 bytes	4 bytes	4 bytes	4 bytes	L_x bytes	L_y bytes	L_z bytes

DSA key pair material format

Key Algorithm	Key Size	Private Key x Length L_x	Public Key y Length L_y	Prime Number p Length L_p	Prime Factor q Length L_q	g length (L_g)	x	y	p	q	g
4 bytes	4 bytes	4 bytes	4 bytes	4 bytes	4 bytes	4 bytes	L_x bytes	L_y bytes	L_p bytes	L_q bytes	L_g bytes

DH key pair material format

Key
Algorithm Key
Size Public Key (pk)
Length L_pk Private Key (sk)
Length L_sk Reserved
Field pk sk

4 bytes 4 bytes 4 bytes 4 bytes 4 bytes L_pk bytes L_sk bytes
Curve25519 key pair material format

Key
Algorithm Key
Size Public Key (pk)
Length L_pk Private Key (sk)
Length L_sk Reserved
Field pk sk

4 bytes 4 bytes 4 bytes 4 bytes 4 bytes L_pk bytes L_sk bytes

Key Algorithm	Key Size	Public Key (pk) Length L_pk	Private Key (sk) Length L_sk	Reserved Field	pk	sk
4 bytes	4 bytes	4 bytes	4 bytes	4 bytes	L_pk bytes	L_sk bytes

Key Algorithm	Key Size	Public Key (pk) Length L_pk	Private Key (sk) Length L_sk	Reserved Field	pk	sk
4 bytes	4 bytes	4 bytes	4 bytes	4 bytes	L_pk bytes	L_sk bytes

Public Key Material Format

When a public key is exported or imported, the key material is encapsulated in the DER format defined in X.509.

The following is ECC public key in DER format:

let eccP256PubKey = new Uint8Array([
    0x30, 0x59, 0x30, 0x13, 0x06, 0x07, 0x2a, 0x86, 0x48, 0xce, 0x3d, 0x02, 0x01, 0x06, 0x08, 0x2a,
    0x86, 0x48, 0xce, 0x3d, 0x03, 0x01, 0x07, 0x03, 0x42, 0x00, 0x04, 0xc0, 0xfe, 0x1c, 0x67, 0xde,
    0x86, 0x0e, 0xfb, 0xaf, 0xb5, 0x85, 0x52, 0xb4, 0x0e, 0x1f, 0x6c, 0x6c, 0xaa, 0xc5, 0xd9, 0xd2,
    0x4d, 0xb0, 0x8a, 0x72, 0x24, 0xa1, 0x99, 0xaf, 0xfc, 0x3e, 0x55, 0x5a, 0xac, 0x99, 0x3d, 0xe8,
    0x34, 0x72, 0xb9, 0x47, 0x9c, 0xa6, 0xd8, 0xfb, 0x00, 0xa0, 0x1f, 0x9f, 0x7a, 0x41, 0xe5, 0x44,
    0x3e, 0xb2, 0x76, 0x08, 0xa2, 0xbd, 0xe9, 0x41, 0xd5, 0x2b, 0x9e
]);

Private Key Material Format

The private key material is in the same format as the key pair material. When the private key material is encapsulated, the public key length in the header of the key pair material is set to 0 and key pair material content and the private key material content are combined.

Private key material = Key pair material header + Private key material content

The following is an example of the RSA private key material.

priKey

let rsa2048PrivateKeyMaterial = new Uint8Array([
    0x01, 0x00, 0x00, 0x00, // Key algorithm: huks.HuksKeyAlg.HUKS_ALG_RSA = 1
    0x00, 0x08, 0x00, 0x00, // Key size (bit): 2048
    0x00, 0x01, 0x00, 0x00, // Length of modulus n (byte): 256
    0x00, 0x00, 0x00, 0x00, // Length of the public key exponent e (byte): 0
    0x00, 0x01, 0x00, 0x00, // Length of the private key exponent d (byte): 256
    // Modulus n
    0xc5, 0x35, 0x62, 0x48, 0xc4, 0x92, 0x87, 0x73, 0x0d, 0x42, 0x96, 0xfc, 0x7b, 0x11, 0x05, 0x06,
    0x0f, 0x8d, 0x66, 0xc1, 0x0e, 0xad, 0x37, 0x44, 0x92, 0x95, 0x2f, 0x6a, 0x55, 0xba, 0xec, 0x1d,
    0x54, 0x62, 0x0a, 0x4b, 0xd3, 0xc7, 0x05, 0xe4, 0x07, 0x40, 0xd9, 0xb7, 0xc2, 0x12, 0xcb, 0x9a,
    0x90, 0xad, 0xe3, 0x24, 0xe8, 0x5e, 0xa6, 0xf8, 0xd0, 0x6e, 0xbc, 0xd1, 0x69, 0x7f, 0x6b, 0xe4,
    0x2b, 0x4e, 0x1a, 0x65, 0xbb, 0x73, 0x88, 0x6b, 0x7c, 0xaf, 0x7e, 0xd0, 0x47, 0x26, 0xeb, 0xa5,
    0xbe, 0xd6, 0xe8, 0xee, 0x9c, 0xa5, 0x66, 0xa5, 0xc9, 0xd3, 0x25, 0x13, 0xc4, 0x0e, 0x6c, 0xab,
    0x50, 0xb6, 0x50, 0xc9, 0xce, 0x8f, 0x0a, 0x0b, 0xc6, 0x28, 0x69, 0xe9, 0x83, 0x69, 0xde, 0x42,
    0x56, 0x79, 0x7f, 0xde, 0x86, 0x24, 0xca, 0xfc, 0xaa, 0xc0, 0xf3, 0xf3, 0x7f, 0x92, 0x8e, 0x8a,
    0x12, 0x52, 0xfe, 0x50, 0xb1, 0x5e, 0x8c, 0x01, 0xce, 0xfc, 0x7e, 0xf2, 0x4f, 0x5f, 0x03, 0xfe,
    0xa7, 0xcd, 0xa1, 0xfc, 0x94, 0x52, 0x00, 0x8b, 0x9b, 0x7f, 0x09, 0xab, 0xa8, 0xa4, 0xf5, 0xb4,
    0xa5, 0xaa, 0xfc, 0x72, 0xeb, 0x17, 0x40, 0xa9, 0xee, 0xbe, 0x8f, 0xc2, 0xd1, 0x80, 0xc2, 0x0d,
    0x44, 0xa9, 0x59, 0x44, 0x59, 0x81, 0x3b, 0x5d, 0x4a, 0xde, 0xfb, 0xae, 0x24, 0xfc, 0xa3, 0xd9,
    0xbc, 0x57, 0x55, 0xc2, 0x26, 0xbc, 0x19, 0xa7, 0x9a, 0xc5, 0x59, 0xa3, 0xee, 0x5a, 0xef, 0x41,
    0x80, 0x7d, 0xf8, 0x5e, 0xc1, 0x1d, 0x32, 0x38, 0x41, 0x5b, 0xb6, 0x92, 0xb8, 0xb7, 0x03, 0x0d,
    0x3e, 0x59, 0x0f, 0x1c, 0xb3, 0xe1, 0x2a, 0x95, 0x1a, 0x3b, 0x50, 0x4f, 0xc4, 0x1d, 0xcf, 0x73,
    0x7c, 0x14, 0xca, 0xe3, 0x0b, 0xa7, 0xc7, 0x1a, 0x41, 0x4a, 0xee, 0xbe, 0x1f, 0x43, 0xdd, 0xf9,
    // Private key exponent d
    0x88, 0x4b, 0x82, 0xe7, 0xe3, 0xe3, 0x99, 0x75, 0x6c, 0x9e, 0xaf, 0x17, 0x44, 0x3e, 0xd9, 0x07,
    0xfd, 0x4b, 0xae, 0xce, 0x92, 0xc4, 0x28, 0x44, 0x5e, 0x42, 0x79, 0x08, 0xb6, 0xc3, 0x7f, 0x58,
    0x2d, 0xef, 0xac, 0x4a, 0x07, 0xcd, 0xaf, 0x46, 0x8f, 0xb4, 0xc4, 0x43, 0xf9, 0xff, 0x5f, 0x74,
    0x2d, 0xb5, 0xe0, 0x1c, 0xab, 0xf4, 0x6e, 0xd5, 0xdb, 0xc8, 0x0c, 0xfb, 0x76, 0x3c, 0x38, 0x66,
    0xf3, 0x7f, 0x01, 0x43, 0x7a, 0x30, 0x39, 0x02, 0x80, 0xa4, 0x11, 0xb3, 0x04, 0xd9, 0xe3, 0x57,
    0x23, 0xf4, 0x07, 0xfc, 0x91, 0x8a, 0xc6, 0xcc, 0xa2, 0x16, 0x29, 0xb3, 0xe5, 0x76, 0x4a, 0xa8,
    0x84, 0x19, 0xdc, 0xef, 0xfc, 0xb0, 0x63, 0x33, 0x0b, 0xfa, 0xf6, 0x68, 0x0b, 0x08, 0xea, 0x31,
    0x52, 0xee, 0x99, 0xef, 0x43, 0x2a, 0xbe, 0x97, 0xad, 0xb3, 0xb9, 0x66, 0x7a, 0xae, 0xe1, 0x8f,
    0x57, 0x86, 0xe5, 0xfe, 0x14, 0x3c, 0x81, 0xd0, 0x64, 0xf8, 0x86, 0x1a, 0x0b, 0x40, 0x58, 0xc9,
    0x33, 0x49, 0xb8, 0x99, 0xc6, 0x2e, 0x94, 0x70, 0xee, 0x09, 0x88, 0xe1, 0x5c, 0x4e, 0x6c, 0x22,
    0x72, 0xa7, 0x2a, 0x21, 0xdd, 0xd7, 0x1d, 0xfc, 0x63, 0x15, 0x0b, 0xde, 0x06, 0x9c, 0xf3, 0x28,
    0xf3, 0xac, 0x4a, 0xa8, 0xb5, 0x50, 0xca, 0x9b, 0xcc, 0x0a, 0x04, 0xfe, 0x3f, 0x98, 0x68, 0x81,
    0xac, 0x24, 0x53, 0xea, 0x1f, 0x1c, 0x6e, 0x5e, 0xca, 0xe8, 0x31, 0x0d, 0x08, 0x12, 0xf3, 0x26,
    0xf8, 0x5e, 0xeb, 0x10, 0x27, 0xae, 0xaa, 0xc3, 0xad, 0x6c, 0xc1, 0x89, 0xdb, 0x7d, 0x5a, 0x12,
    0x55, 0xad, 0x11, 0x19, 0xa1, 0xa9, 0x8f, 0x0b, 0x6d, 0x78, 0x8d, 0x1c, 0xdf, 0xe5, 0x63, 0x82,
    0x0b, 0x7d, 0x23, 0x04, 0xb4, 0x75, 0x8c, 0xed, 0x77, 0xfc, 0x1a, 0x85, 0x29, 0x11, 0xe0, 0x61,
]);