Source file src/golang.org/x/crypto/curve25519/curve25519_go120.go

Documentation: golang.org/x/crypto/curve25519

     1  // Copyright 2022 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:build go1.20
     6  
     7  package curve25519
     8  
     9  import "crypto/ecdh"
    10  
    11  func x25519(dst *[32]byte, scalar, point []byte) ([]byte, error) {
    12  	curve := ecdh.X25519()
    13  	pub, err := curve.NewPublicKey(point)
    14  	if err != nil {
    15  		return nil, err
    16  	}
    17  	priv, err := curve.NewPrivateKey(scalar)
    18  	if err != nil {
    19  		return nil, err
    20  	}
    21  	out, err := priv.ECDH(pub)
    22  	if err != nil {
    23  		return nil, err
    24  	}
    25  	copy(dst[:], out)
    26  	return dst[:], nil
    27  }
    28  
    29  func scalarMult(dst, scalar, point *[32]byte) {
    30  	if _, err := x25519(dst, scalar[:], point[:]); err != nil {
    31  		// The only error condition for x25519 when the inputs are 32 bytes long
    32  		// is if the output would have been the all-zero value.
    33  		for i := range dst {
    34  			dst[i] = 0
    35  		}
    36  	}
    37  }
    38  
    39  func scalarBaseMult(dst, scalar *[32]byte) {
    40  	curve := ecdh.X25519()
    41  	priv, err := curve.NewPrivateKey(scalar[:])
    42  	if err != nil {
    43  		panic("curve25519: internal error: scalarBaseMult was not 32 bytes")
    44  	}
    45  	copy(dst[:], priv.PublicKey().Bytes())
    46  }
    47  

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