Signatures

TKeeper provides threshold-based digital signatures using secure multiparty computation (MPC).
Each operation is distributed — no full private key is ever reconstructed on any node.

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Supported Signature Schemes

Session Type	Curve	Signature Algorithm
GG20	SECP256K1	ECDSA
FROST	SECP256K1	SCHNORR
FROST	ED25519	SCHNORR

• Signature type is determined based on sessionType + curve
• You may override the type for verification explicitly using sigType

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Authorization

Signing and verification require fine-grained permissions.

Required Permissions

Action	Permission
Sign	tkeeper.key.{keyId}.sign
Verify	tkeeper.key.{keyId}.verify
Public Key	tkeeper.key.{keyId}.public (if used)

See auth.md for full permission list and structure.

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Signing

Endpoint

POST /v1/keeper/sign

Performs a threshold signature over one or more messages.

Request Body

{
  "keyId": "my-key-id",
  "type": "GG20",
  "operations": {
    "message1": "base64-encoded data",
    "message2": "base64-encoded data"
  }
}

Fields

• keyId: identifier of the key to sign with
• type: session type (GG20 or FROST)
• operations: map of operation ID → base64-encoded message

Constraints

• For GG20: only one operation is allowed
• For FROST: multiple operations are supported in a single request

This reflects the protocol behavior: GG20 is round-heavy and supports only one message per session.

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Verification

Endpoint

POST /v1/keeper/sign/verify

Verifies a signature against a key.

Request Body

{
  "keyId": "my-key-id",
  "data64": "base64-encoded message",
  "signature64": "base64-encoded signature"
}

Fields

• keyId: key to verify against
• data64: base64-encoded original message
• signature64: base64-encoded signature

Response

{
  "valid": true
}

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Signature Response Format

Signature Result (/sign)

{
  "code": "SUCCESS",
  "signature": {
    "message1": "base64-encoded signature",
    "message2": "base64-encoded signature"
  }
}

• code: SUCCESS or FAILED
• signature: map of operation ID → base64-encoded signature

Each operation ID matches the one used in the operations field of the request.

GG20 always returns a single operation.

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Signature Encoding

All signatures are raw byte arrays, base64-encoded.

ECDSA (via GG20)

• Format: r || s || recId
• Size: 65 bytes
  • r: 32 bytes
  • s: 32 bytes
  • recId: 1 byte (0–3)

⚠ Not DER-encoded. This is the uncompressed ECDSA format with recovery ID, commonly used in Ethereum.

SCHNORR (via FROST)

• Format: r || s
• Size: 64 bytes
  • r: 32 bytes
  • s: 32 bytes

Standard Schnorr signature format (e.g., BIP-340 / EdDSA compatible).