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## javacard.security
Interface ECKey

All Known Subinterfaces:
  ECPrivateKey, ECPublicKey

    @TransactionType(value=SUPPORTS)
    public interface ECKey

The `ECKey` interface is the base interface for the EC algorithm's private and public key implementations. An EC private key implementation must also implement the `ECPrivateKey` interface methods. An EC public key implementation must also implement the `ECPublicKey` interface methods.

The equation of the curves for keys of type `TYPE_EC_FP_PUBLIC` or `TYPE_EC_FP_PRIVATE` is y^2 = x^3 + A * x + B. The equation of the curves for keys of type `TYPE_EC_F2M_PUBLIC` or `TYPE_EC_F2M_PRIVATE` is y^2 + x * y = x^3 + A * x^2 + B.

The notation used to describe parameters specific to the EC algorithm is based on the naming conventions established in [IEEE P1363].

See Also:
  `ECPublicKey`, `ECPrivateKey`, `KeyBuilder`, `Signature`, `javacardx.crypto.KeyEncryption`, `KeyAgreement`

Method Summary
`short` | `getA(byte[] buffer, short offset)` Returns the first coefficient of the curve of the key.
`short` | `getB(byte[] buffer, short offset)` Returns the second coefficient of the curve of the key.
`short` | `getField(byte[] buffer, short offset)` Returns the field specification parameter value of the key.
`short` | `getG(byte[] buffer, short offset)` Returns the fixed point of the curve.
`short` | `getK()` Returns the cofactor of the order of the fixed point G of the curve.
`short` | `getR(byte[] buffer, short offset)` Returns the order of the fixed point G of the curve.
`void` | `setA(byte[] buffer, short offset, short length)` Sets the first coefficient of the curve of the key.
`void` | `setB(byte[] buffer, short offset, short length)` Sets the second coefficient of the curve of the key.
`void` | `setFieldF2M(short e)` Sets the field specification parameter value for keys of type `TYPE_EC_F2M_PUBLIC` or `TYPE_EC_F2M_PRIVATE` in the case where the polynomial is a trinomial, of the form x^n + x^e + 1 (where n is the bit length of the key).
`void` | `setFieldF2M(short e1, short e2, short e3)` Sets the field specification parameter value for keys of type `TYPE_EC_F2M_PUBLIC` or `TYPE_EC_F2M_PRIVATE` in the case where the polynomial is a pentanomial, of the form x^n + x^e1 + x^e2 + x^e3 + 1 (where n is the bit length of the key).
`void` | `setFieldFP(byte[] buffer, short offset, short length)` Sets the field specification parameter value for keys of type `TYPE_EC_FP_PRIVATE` or `TYPE_EC_FP_PUBLIC`.
`void` | `setG(byte[] buffer, short offset, short length)` Sets the fixed point of the curve.
`void` | `setK(short K)` Sets the cofactor of the order of the fixed point G of the curve.
`void` | `setR(byte[] buffer, short offset, short length)` Sets the order of the fixed point G of the curve.

Method Detail

### setFieldFP

    void setFieldFP(byte[] buffer,
                    short offset,
                    short length)
                    throws CryptoException

  Sets the field specification parameter value for keys of type `TYPE_EC_FP_PRIVATE` or `TYPE_EC_FP_PUBLIC`. The specified value is the prime p corresponding to the field GF(p). The plain text data format is big-endian and right-aligned (the least significant bit is the least significant bit of last byte). Input parameter data is copied into the internal representation.

  Note:

  - If the key object implements the `javacardx.crypto.KeyEncryption` interface and the `Cipher` object specified via `setKeyCipher()` is not `null`, the key value is decrypted using the `Cipher` object.

  Parameters:
    `buffer` - the input buffer
    `offset` - the offset into the input buffer at which the parameter value begins
    `length` - the byte length of the parameter value
  Throws:
    `CryptoException` - with the following reason codes:
    - `CryptoException.ILLEGAL_VALUE` if the length parameter is 0 or invalid or if the input parameter data is inconsistent with the key length or if input data decryption is required and fails.
    - `CryptoException.NO_SUCH_ALGORITHM` if the key is neither of type `TYPE_EC_FP_PUBLIC` nor `TYPE_EC_FP_PRIVATE`.

### setFieldF2M

    void setFieldF2M(short e)
                     throws CryptoException

  Sets the field specification parameter value for keys of type `TYPE_EC_F2M_PUBLIC` or `TYPE_EC_F2M_PRIVATE` in the case where the polynomial is a trinomial, of the form x^n + x^e + 1 (where n is the bit length of the key). It is required that n > e > 0.

  Parameters:
    `e` - the value of the intermediate exponent of the trinomial
  Throws:
    `CryptoException` - with the following reason codes:
    - `CryptoException.ILLEGAL_VALUE` if the input parameter e is not such that 0 < e < n.
    - `CryptoException.NO_SUCH_ALGORITHM` if the key is neither of type `TYPE_EC_F2M_PUBLIC` nor `TYPE_EC_F2M_PRIVATE`.

### setFieldF2M

    void setFieldF2M(short e1,
                     short e2,
                     short e3)
                     throws CryptoException

  Sets the field specification parameter value for keys of type `TYPE_EC_F2M_PUBLIC` or `TYPE_EC_F2M_PRIVATE` in the case where the polynomial is a pentanomial, of the form x^n + x^e1 + x^e2 + x^e3 + 1 (where n is the bit length of the key). It is required for all ei where ei = {e1, e2, e3} that n > ei > 0.

  Parameters:
    `e1` - the value of the first of the intermediate exponents of the pentanomial
    `e2` - the value of the second of the intermediate exponent of the pentanomial
    `e3` - the value of the third of the intermediate exponents
  Throws:
    `CryptoException` - with the following reason codes:
    - `CryptoException.ILLEGAL_VALUE` if the input parameters ei where ei = {`e1`, `e2`, `e3`} are not such that for all ei, n > ei > 0.
    - `CryptoException.NO_SUCH_ALGORITHM` if the key is neither of type `TYPE_EC_F2M_PUBLIC` nor `TYPE_EC_F2M_PRIVATE`.

### setA

    void setA(byte[] buffer,
              short offset,
              short length)
              throws CryptoException

  Sets the first coefficient of the curve of the key. For keys of type `TYPE_EC_FP_PRIVATE` or `TYPE_EC_FP_PUBLIC`, this is the value of A as an integer modulo the field specification parameter p, that is, an integer in the range `0` to p-1. For keys of type `TYPE_EC_F2M_PRIVATE` or `TYPE_EC_F2M_PUBLIC`, the bit representation of this value specifies a polynomial with binary coefficients which represents the value of A in the field. The plain text data format is big-endian and right-aligned (the least significant bit is the least significant bit of last byte). Input parameter data is copied into the internal representation.

  Note:

  - If the key object implements the `javacardx.crypto.KeyEncryption` interface and the `Cipher` object specified via `setKeyCipher()` is not `null`, the key value is decrypted using the `Cipher` object.

  Parameters:
    `buffer` - the input buffer
    `offset` - the offset into the input buffer at which the coefficient value begins
    `length` - the byte length of the coefficient value
  Throws:
    `CryptoException` - with the following reason codes:
    - `CryptoException.ILLEGAL_VALUE` if the length parameter is 0 or invalid or if the input parameter data is inconsistent with the key length or if input data decryption is required and fails.

### setB

    void setB(byte[] buffer,
              short offset,
              short length)
              throws CryptoException

  Sets the second coefficient of the curve of the key. For keys of type `TYPE_EC_FP_PRIVATE` or `TYPE_EC_FP_PUBLIC`, this is the value of B as an integer modulo the field specification parameter p, that is, an integer in the range `0` to p-1. For keys of type `TYPE_EC_F2M_PRIVATE` or `TYPE_EC_F2M_PUBLIC`, the bit representation of this value specifies a polynomial with binary coefficients which represents the value of B in the field. The plain text data format is big-endian and right-aligned (the least significant bit is the least significant bit of last byte). Input parameter data is copied into the internal representation.

  Note:

  - If the key object implements the `javacardx.crypto.KeyEncryption` interface and the `Cipher` object specified via `setKeyCipher()` is not `null`, the key value is decrypted using the `Cipher` object.

  Parameters:
    `buffer` - the input buffer
    `offset` - the offset into the input buffer at which the coefficient value begins
    `length` - the byte length of the coefficient value
  Throws:
    `CryptoException` - with the following reason codes:
    - `CryptoException.ILLEGAL_VALUE` if the length parameter is 0 or invalid or if the input parameter data is inconsistent with the key length or if input data decryption is required and fails.

### setG

    void setG(byte[] buffer,
              short offset,
              short length)
              throws CryptoException

  Sets the fixed point of the curve. The point should be specified as an octet string as per ANSI X9.62. A specific implementation need not support the compressed form, but must support the uncompressed form of the point. The plain text data format is big-endian and right-aligned (the least significant bit is the least significant bit of last byte). Input parameter data is copied into the internal representation.

  Note:

  - If the key object implements the `javacardx.crypto.KeyEncryption` interface and the `Cipher` object specified via `setKeyCipher()` is not `null`, the key value is decrypted using the `Cipher` object.

  Parameters:
    `buffer` - the input buffer
    `offset` - the offset into the input buffer at which the point specification begins
    `length` - the byte length of the point specification
  Throws:
    `CryptoException` - with the following reason codes:
    - `CryptoException.ILLEGAL_VALUE` if the length parameter is 0 or invalid or if the input parameter data format is incorrect, or if the input parameter data is inconsistent with the key length, or if input data decryption is required and fails.

### setR

    void setR(byte[] buffer,
              short offset,
              short length)
              throws CryptoException

  Sets the order of the fixed point G of the curve. The plain text data format is big-endian and right-aligned (the least significant bit is the least significant bit of last byte). Input parameter data is copied into the internal representation.

  Parameters:
    `buffer` - the input buffer
    `offset` - the offset into the input buffer at which the order begins
    `length` - the byte length of the order
  Throws:
    `CryptoException` - with the following reason codes:
    - `CryptoException.ILLEGAL_VALUE` if the length parameter is 0 or invalid or if the input parameter data is inconsistent with the key length, or if input data decryption is required and fails.

    Note:

    - If the key object implements the `javacardx.crypto.KeyEncryption` interface and the `Cipher` object specified via `setKeyCipher()` is not `null`, the key value is decrypted using the `Cipher` object.

### setK

    void setK(short K)

  Sets the cofactor of the order of the fixed point G of the curve. The cofactor need not be specified for the key to be initialized. However, the `KeyAgreement` algorithm type `ALG_EC_SVDP_DHC` requires that the cofactor, K, be initialized.

  Parameters:
    `K` - the value of the cofactor

### getField

    short getField(byte[] buffer,
                   short offset)
                   throws CryptoException

  Returns the field specification parameter value of the key. For keys of type `TYPE_EC_FP_PRIVATE` or `TYPE_EC_FP_PUBLIC`, this is the value of the prime p corresponding to the field GF(p). For keys of type `TYPE_EC_F2M_PRIVATE` or `TYPE_EC_F2M_PUBLIC`, it is the value whose bit representation specifies the polynomial with binary coefficients used to define the arithmetic operations in the field GF(2^n) The plain text data format is big-endian and right-aligned (the least significant bit is the least significant bit of last byte).

  Parameters:
    `buffer` - the output buffer
    `offset` - the offset into the output buffer at which the parameter value is to begin
  Returns:
    the byte length of the parameter
  Throws:
    `CryptoException` - with the following reason code:
    - `CryptoException.UNINITIALIZED_KEY` if the field specification parameter value of the key has not been successfully initialized since the time the initialized state of the key was set to false.
  See Also:
    `Key`

### getA

    short getA(byte[] buffer,
               short offset)
               throws CryptoException

  Returns the first coefficient of the curve of the key. For keys of type `TYPE_EC_FP_PRIVATE` or `TYPE_EC_FP_PUBLIC`, this is the value of A as an integer modulo the field specification parameter p, that is, an integer in the range `0` to p-1. For keys of type `TYPE_EC_F2M_PRIVATE` or `TYPE_EC_F2M_PUBLIC`, the bit representation of this value specifies a polynomial with binary coefficients which represents the value of A in the field. The plain text data format is big-endian and right-aligned (the least significant bit is the least significant bit of last byte).

  Parameters:
    `buffer` - the output buffer
    `offset` - the offset into the output buffer at which the coefficient value is to begin
  Returns:
    the byte length of the coefficient
  Throws:
    `CryptoException` - with the following reason code:
    - `CryptoException.UNINITIALIZED_KEY` if the coefficient of the curve of the key has not been successfully initialized since the time the initialized state of the key was set to false.
  See Also:
    `Key`

### getB

    short getB(byte[] buffer,
               short offset)
               throws CryptoException

  Returns the second coefficient of the curve of the key. For keys of type `TYPE_EC_FP_PRIVATE` or `TYPE_EC_FP_PUBLIC`, this is the value of B as an integer modulo the field specification parameter p, that is, an integer in the range 0 to p-1. For keys of type `TYPE_EC_F2M_PRIVATE` or `TYPE_EC_F2M_PUBLIC`, the bit representation of this value specifies a polynomial with binary coefficients which represents the value of B in the field. The plain text data format is big-endian and right-aligned (the least significant bit is the least significant bit of last byte).

  Parameters:
    `buffer` - the output buffer
    `offset` - the offset into the output buffer at which the coefficient value is to begin
  Returns:
    the byte length of the coefficient
  Throws:
    `CryptoException` - with the following reason code:
    - `CryptoException.UNINITIALIZED_KEY` if the second coefficient of the curve of the key has not been successfully initialized since the time the initialized state of the key was set to false.
  See Also:
    `Key`

### getG

    short getG(byte[] buffer,
               short offset)
               throws CryptoException

  Returns the fixed point of the curve. The point is represented as an octet string in compressed or uncompressed forms as per ANSI X9.62. The plain text data format is big-endian and right-aligned (the least significant bit is the least significant bit of last byte).

  Parameters:
    `buffer` - the output buffer
    `offset` - the offset into the output buffer at which the point specification data is to begin
  Returns:
    the byte length of the point specification
  Throws:
    `CryptoException` - with the following reason code:
    - `CryptoException.UNINITIALIZED_KEY` if the fixed point of the curve of the key has not been successfully initialized since the time the initialized state of the key was set to false.
  See Also:
    `Key`

### getR

    short getR(byte[] buffer,
               short offset)
               throws CryptoException

  Returns the order of the fixed point G of the curve. The plain text data format is big-endian and right-aligned (the least significant bit is the least significant bit of last byte).

  Parameters:
    `buffer` - the output buffer
    `offset` - the offset into the input buffer at which the order begins
  Returns:
    the byte length of the order
  Throws:
    `CryptoException` - with the following reason code:
    - `CryptoException.UNINITIALIZED_KEY` if the order of the fixed point G of the curve of the key has not been successfully initialized since the time the initialized state of the key was set to false.
  See Also:
    `Key`

### getK

    short getK()
               throws CryptoException

  Returns the cofactor of the order of the fixed point G of the curve.

  Returns:
    the value of the cofactor
  Throws:
    `CryptoException` - with the following reason codes:
    - `CryptoException.UNINITIALIZED_KEY` if the cofactor of the order of the fixed point G of the curve of the key has not been successfully initialized since the time the initialized state of the key was set to false.
  See Also:
    `Key`

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