OpenSSL EC

ecdsa.cr

# http://fm4dd.com/openssl/eckeycreate.htm
# https://stackoverflow.com/questions/34404427/how-do-i-check-if-an-evp-pkey-contains-a-private-key
# https://davidederosa.com/basic-blockchain-programming/elliptic-curve-keys/

lib LibSSL
  fun EC_KEY_generate_key(key : LibC::Int*) : LibC::Int
  fun EC_KEY_new_by_curve_name(i : LibC::Int) : LibC::Int*
  fun OBJ_txt2nid(s : LibC::Char*) : LibC::Int
  fun EVP_PKEY_new : LibC::Int*
  fun EVP_PKEY_assign(pkey : LibC::Int*, type : LibC::Int, key : Void*) : LibC::Int
  alias EcKeySt = Void
  alias EVP_PKEY = Void*
  alias EC_KEY = Void*
  alias EcPoint = Void*

  fun EVP_PKEY_get1_EC_KEY(pkey : LibC::Int*) : EcKeySt*
  fun EVP_PKEY_bits(pkey : LibC::Int*) : LibC::Int
  fun EC_KEY_get0_private_key(pkey : LibC::Int*) : LibC::Int*
  fun EC_KEY_get0_public_key(key : LibC::Int*) : EcPoint

  fun BN_bn2hex(a : LibC::Int*) : LibC::Char*
  fun BN_bn2dec(a : LibC::Int*) : LibC::Char*

  type EcGroup = Void*
  enum PointConversionFormT
    PointConversionCompressed = 2
    PointConversionUncompressed = 4
    PointConversionHybrid = 6
  end
  fun EC_POINT_point2hex(x0 : EcGroup, x1 : EcPoint, form : PointConversionFormT) : LibC::Char*
  fun EC_GROUP_new_by_curve_name(nid : LibC::Int) : EcGroup

  fun EC_KEY_free(key : LibC::Int*)
  fun EC_POINT_free(point : EcPoint)
  fun EC_GROUP_free(group : EcGroup)
end

# Create a EC key sructure, setting the group type from NID
eccgrp = LibSSL.OBJ_txt2nid("secp256k1")
myecc = LibSSL.EC_KEY_new_by_curve_name(eccgrp);

# Create the public/private EC key pair here
LibSSL.EC_KEY_generate_key(myecc)

# Get the private key
bn = LibSSL.EC_KEY_get0_private_key(myecc)
private_key_pointer = LibSSL.BN_bn2hex(bn)
private_key = String.new(private_key_pointer).downcase
puts private_key

# Get the public key
ec_point = LibSSL.EC_KEY_get0_public_key(myecc)
form = LibSSL::PointConversionFormT::PointConversionUncompressed
grp = LibSSL.EC_GROUP_new_by_curve_name(eccgrp)
public_key_pointer = LibSSL.EC_POINT_point2hex(grp, ec_point, form)
public_key = String.new(public_key_pointer).downcase
puts public_key

# Free up mem
LibSSL.EC_KEY_free(myecc);
LibSSL.EC_GROUP_free(grp)