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51 .Dd $Mdocdate: December 11 2016 $
52 .Dt EC_GFP_SIMPLE_METHOD 3
53 .Os
54 .Sh NAME
55 .Nm EC_GFp_simple_method ,
56 .Nm EC_GFp_mont_method ,
57 .Nm EC_GFp_nist_method ,
58 .Nm EC_GFp_nistp224_method ,
59 .Nm EC_GFp_nistp256_method ,
60 .Nm EC_GFp_nistp521_method ,
61 .Nm EC_GF2m_simple_method ,
62 .Nm EC_METHOD_get_field_type
63 .Nd obtain EC_METHOD objects
64 .Sh SYNOPSIS
65 .In openssl/ec.h
66 .Ft const EC_METHOD *
67 .Fn EC_GFp_simple_method void
68 .Ft const EC_METHOD *
69 .Fn EC_GFp_mont_method void
70 .Ft const EC_METHOD *
71 .Fn EC_GFp_nist_method void
72 .Ft const EC_METHOD *
73 .Fn EC_GFp_nistp224_method void
74 .Ft const EC_METHOD *
75 .Fn EC_GFp_nistp256_method void
76 .Ft const EC_METHOD *
77 .Fn EC_GFp_nistp521_method void
78 .Ft const EC_METHOD *
79 .Fn EC_GF2m_simple_method void
80 .Ft int
81 .Fo EC_METHOD_get_field_type
82 .Fa "const EC_METHOD *meth"
83 .Fc
84 .Sh DESCRIPTION
85 The elliptic curve library provides a number of different
86 implementations through a single common interface.
87 Each implementation is optimised for different scenarios.
88 An implementation is represented by an
89 .Vt EC_METHOD
90 structure.
91 .Pp
92 When constructing a curve using
93 .Xr EC_GROUP_new 3 ,
94 an implementation method must be provided.
95 The functions described here all return a const pointer to an
96 .Sy EC_METHOD
97 structure that can be passed to
98 .Xr EC_GROUP_new 3 .
99 It is important that the correct implementation type for the form
100 of curve selected is used.
101 .Pp
102 For F2^m curves there is only one implementation choice,
103 .Fn EC_GF2_simple_method .
104 .Pp
105 For Fp curves the lowest common denominator implementation is the
106 .Fn EC_GFp_simple_method
107 implementation.
108 All other implementations are based on this one.
109 .Fn EC_GFp_mont_method
110 adds the use of Montgomery multiplication (see
111 .Xr BN_mod_mul_montgomery 3 ) .
112 .Fn EC_GFp_nist_method
113 offers an implementation optimised for use with NIST recommended
114 curves.
115 NIST curves are available through
116 .Xr EC_GROUP_new_by_curve_name 3 .
117 .Pp
118 The functions
119 .Fn EC_GFp_nistp224_method ,
120 .Fn EC_GFp_nistp256_method ,
121 and
122 .Fn EC_GFp_nistp521_method
123 offer 64-bit optimised implementations for the NIST P224, P256 and
124 P521 curves respectively.
125 Note, however, that these implementations are not available on all
126 platforms.
127 .Pp
128 .Fn EC_METHOD_get_field_type
129 identifies what type of field the
130 .Vt EC_METHOD
131 structure supports, which will be either F2^m or Fp.
132 If the field type is Fp, then the value
133 .Dv NID_X9_62_prime_field
134 is returned.
135 If the field type is F2^m, then the value
136 .Dv NID_X9_62_characteristic_two_field
137 is returned.
138 These values are defined in the
139 .In openssl/obj_mac.h
140 header file.
141 .Sh RETURN VALUES
142 All
143 .Fn EC_GFp*
144 functions and
145 .Fn EC_GF2m_simple_method
146 always return a const pointer to an
147 .Vt EC_METHOD
148 structure.
149 .Pp
150 .Fn EC_METHOD_get_field_type
151 returns an integer that identifies the type of field the
152 .Vt EC_METHOD
153 structure supports.
154 .Sh SEE ALSO
155 .Xr BN_mod_mul_montgomery 3 ,
156 .Xr d2i_ECPKParameters 3 ,
157 .Xr EC_GROUP_copy 3 ,
158 .Xr EC_GROUP_new 3 ,
159 .Xr EC_KEY_new 3 ,
160 .Xr EC_POINT_add 3 ,
161 .Xr EC_POINT_new 3