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I am trying to set the ECC private key explicitly with mbedTLS for ECDSA signing. The key has been generated externally from mbedTLS and consists of the following arrays for the private key and the public key in the NIST secp256r1 curve (below). In all the of the mbedTLS ECDSA exmaples that I have seen, the key is generated with a random number generator with mbedtls_ecp_gen_key() but this doesn't work for me since I need to generate the key pair outside of the code and then set explicitly in the code.

const uint8_t Private_Key[] =
{
    0x0a, 0x75, 0xde, 0x36, 0x78, 0x73, 0x50, 0x8b, 0x25, 0x1e, 0x19, 0xbe, 0xf4, 0x7b, 0x74,
    0xfc, 0xd6, 0x97, 0x44, 0x12, 0x5f, 0x1c, 0x49, 0x89, 0x98, 0x0b, 0x65, 0x6c, 0x48, 0xa7, 0x8c, 0x5c

};


const uint8_t Public_Key[] =
{
    0x3b, 0x08, 0xd7, 0x1a, 0x1b, 0x5a, 0xd0, 0x3e, 0x41, 0x5d, 0x8f, 0x68, 0xe9, 0x78,0x47, 0x6b,
    0x35, 0x5c, 0xe2, 0x90, 0x8d, 0xb9, 0xc1, 0x46, 0xb1, 0x44, 0x77, 0x1f, 0x92, 0x57, 0xbf, 0x8e,
    0x7c, 0xed, 0xdf, 0x3b, 0xea, 0xed, 0x5d, 0xea, 0x1d, 0x77, 0x39, 0xdb, 0xb7, 0x42, 0xe3, 0x6a,
    0x07, 0x74, 0xca, 0x50, 0x8b, 0x19, 0xf5, 0x37, 0xd5, 0x2d, 0x57, 0x71, 0x70, 0x7e, 0xc7, 0x16
};
Gerhardh
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Rohit Khera
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1 Answers1

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You can have a look at mbedtls_ecp_read_key for importing secret key and mbedtls_ecp_point_read_binary for importing public key from key data generated outside. Notice that mbedtls_ecp_point_read_binary expects binary data in uncompressed public key format, i.e 0x04 followed by X followed by Y, which means you should add a 0x04 to the head of the Public_Key data in your code.

IsMeJane
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