private byte[] makeHpkeSuiteId() {
        byte[] hpkePrefix = new byte[] { 'H','P','K','E' };
        return concat(hpkePrefix, i2osp2(kem.kemId()), i2osp2(kdf.kdfId()), i2osp2(aead.aeadId()));
    }
Section 5.1 Creating the Encryption Context:

HPKE implicit suite_id (this differs from the KEM suite id):

<pre>
suite_id = concat(
  "HPKE",
  I2OSP(kem_id, 2),
  I2OSP(kdf_id, 2),
  I2OSP(aead_id, 2)
)
</pre>
security-utils/src/main/java/com/yahoo/security/hpke/Hpke.java