ECDH Group 19 (256-bit Elliptic curve) key length

[Vishal Kevat]

Hi OpenSSL,

I am using group 19 which is ECDH elliptic curve group (NID_X9_62_prime256v1) and is giving 32 bytes/256 bit of shared secret key.

I want to use it to work with AES-128 CBC encryption algorithm. As the key length generated by ECDH is 32 bytes, is there any way to generate the key length of 16 bytes/128 bit with group 19 ECDH algorithm?

On one of the article, it is mentioned that encryption or authentication algorithms with a 128-bit key to be used for Diffie-Hellman groups 5, 14, 19, 20 or 24.
Link: https://community.cisco.com/t5/security-knowledge-base/diffie-hellman-groups/ta-p/3147010
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Please let me know if group 19 can generate 128 bit key length by any means.

Regards,
Vishal Kevat




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