This test data was produced by creating a self-signed EC cert using OpenSSL,
and then extracting the relevant fields.

It uses ECDSA with curve secp384r1 an SHA-256.

(1) Generate self-signed certificate

  openssl ecparam -out ec_key.pem -name secp384r1 -genkey 
  openssl req -new -key ec_key.pem -x509 -nodes -days 365 -out cert.pem

(2) Extract public key

  openssl x509 -in cert.pem -pubkey -noout > pubkey.pem
  cat pubkey.pem

(3) Extract signed data (tbsCertificate)

  openssl asn1parse -in cert.pem -out tbs -noout -strparse 4
  base64 tbs

(4) Extract signature algorithm

  # Find the offset of the signature algorithm near the end (496 in this case)
  openssl asn1parse -in cert.pem

  openssl asn1parse -in cert.pem -out alg -noout -strparse 496
  base64 alg

(5) Extract the signature

  # Find the final offset of BIT STRING (508 in this case)
  openssl asn1parse -in cert.pem

  openssl asn1parse -in cert.pem -out sig -noout -strparse 508
  base64 sig


$ openssl asn1parse -i < [PUBLIC KEY]
    0:d=0  hl=2 l= 118 cons: SEQUENCE
    2:d=1  hl=2 l=  16 cons:  SEQUENCE
    4:d=2  hl=2 l=   7 prim:   OBJECT            :id-ecPublicKey
   13:d=2  hl=2 l=   5 prim:   OBJECT            :secp384r1
   20:d=1  hl=2 l=  98 prim:  BIT STRING
-----BEGIN PUBLIC KEY-----
MHYwEAYHKoZIzj0CAQYFK4EEACIDYgAEXFhBi+WKXuxeK9yCbC9jqEchwjCNsQ4RXAsJ07oHZ+Q
qz55cNIY5BAhcQ0QYY5jv9BimGL9SuhUuOSuS3Pn9rrsIFGcFsihy4kDr8rq5+7RbN8bV057gW5
emYjLtvDsQ
-----END PUBLIC KEY-----

$ openssl asn1parse -i < [ALGORITHM]
    0:d=0  hl=2 l=  10 cons: SEQUENCE
    2:d=1  hl=2 l=   8 prim:  OBJECT            :ecdsa-with-SHA256
-----BEGIN ALGORITHM-----
MAoGCCqGSM49BAMC
-----END ALGORITHM-----

-----BEGIN DATA-----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-----END DATA-----

$ openssl asn1parse -i < [SIGNATURE]
    0:d=0  hl=2 l= 105 prim: BIT STRING
-----BEGIN SIGNATURE-----
A2kAMGYCMQCDwMSZVJZ8qThiNTV7VX57m8fdNnNS6cXIjRYoh4SozlYWmWGh87nhmJJCeD16jVM
CMQDkroAY8oNi8RxLUor+LozhhVgu24tu6lcp4MP8H3Zy8bBea5HerAd1AqJp3Ox7KDU=
-----END SIGNATURE-----