SM2 public key from private key
Derive the SM2 public key (Q = d·G) from a private scalar or PKCS#8 PEM — sm2p256v1 (GM/T 0003). Get SEC1 hex and SPKI PEM. Runs in your browser; nothing is uploaded.
About this tool
SM2 public key from private key derives the public key for a private key on
the SM2 elliptic curve — the Chinese national standard GM/T 0003 scheme
mandated by OSCCA, using curve sm2p256v1. The public point is computed as
Q = d·G (one scalar multiplication of the curve's base point), so the result is
fully deterministic — the same private key always yields the same public key.
- Input: a raw 32-byte private scalar in hex (64 hex chars, an optional
0xprefix is fine) or a PKCS#8 PEM (-----BEGIN PRIVATE KEY-----). Leave the format on auto to detect which, or force hex / pem. - Output: choose all for a labelled summary of every encoding, or pick a
single one — uncompressed SEC1 hex (
04 || x || y, 130 chars), compressed SEC1 hex (02|03 || x, 66 chars), or SPKI PEM (-----BEGIN PUBLIC KEY-----). The affine x and y coordinates are also shown.
Privacy
Everything runs in your browser via WebAssembly — your private key never leaves the device. The tool only ever returns public key material; the private key is used solely to compute the public point and is never echoed back. Also available from the gizza CLI and in chat.
Need a new key instead?
If you don't already have a private key, use the sm2-keypair-generate tool to create a fresh SM2 key pair (private + public, PEM + hex) with a secure random number generator.
FAQ
What exactly can I paste as the private key?
Either a raw 32-byte scalar as exactly 64 hex characters (a leading 0x
is fine — anything else in length is rejected), or a PKCS#8 PEM block
starting with -----BEGIN PRIVATE KEY-----. With the input format on
auto the tool detects which one you pasted; set it to hex or pem to
force the interpretation.
Compressed or uncompressed — which output should I use?
They encode the same point: uncompressed SEC1 is 04 ‖ x ‖ y (130 hex
chars), compressed is 02/03 ‖ x (66 hex chars, the prefix records y's
parity). Use whichever your target system expects — many GM/T toolchains
default to uncompressed — or pick all to get both plus the SPKI PEM and
the raw x/y coordinates.
Can I feed in a NIST P-256 private key?
A 32-byte P-256 scalar will be accepted (it's just a number in range), but the point is computed on sm2p256v1, SM2's own curve — so the result is a valid SM2 public key, not your P-256 public key. The two curves are different; use an SM2 key with this tool.
Is my private key ever exposed?
No. Derivation runs entirely in your browser via WebAssembly, and the tool
only returns public key material — the private scalar is used for the
single Q = d·G multiplication and never echoed back or transmitted.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool sm2-public-from-private "3945208F7B2144B13F36E38AC6D39F95889393692860B51A42FB81EF4DF7C5B8"New to the CLI? Get gizza →
Open it by URL
Pre-fill and auto-run this tool with query parameters — the names match the API/CLI:
https://gizza.ai/tools/sm2-public-from-private/?private_key=3945208F7B2144B13F36E38AC6D39F95889393692860B51A42FB81EF4DF7C5B8&input_format=auto&output_format=allMachine-readable descriptor: tool.json — title + parameters JSON Schema for agents.