def _load_and_validate_digest(self, public_keys, bucket, key):
        digest_data, digest = self.digest_provider.fetch_digest(bucket, key)
        for required_key in self.required_digest_keys:
            if required_key not in digest_data:
                raise InvalidDigestFormat(bucket, key)
        # Ensure the bucket and key are the same as what's expected.
        if digest_data['digestS3Bucket'] != bucket \
                or digest_data['digestS3Object'] != key:
            raise DigestError(
                ('Digest file\ts3://%s/%s\tINVALID: has been moved from its '
                 'original location') % (bucket, key))
        # Get the public keys in the given time range.
        fingerprint = digest_data['digestPublicKeyFingerprint']
        if fingerprint not in public_keys:
            raise DigestError(
                ('Digest file\ts3://%s/%s\tINVALID: public key not found in '
                 'region %s for fingerprint %s') %
                (bucket, key, self.digest_provider.trail_home_region,
                 fingerprint))
        public_key_hex = public_keys[fingerprint]['Value']
        self._digest_validator.validate(
            bucket, key, public_key_hex, digest_data, digest)
        end_date = normalize_date(parse_date(digest_data['digestEndTime']))
        return digest_data, end_date
Loads and validates a digest from S3.
dataset/ETHPy150Open aws/aws-cli/awscli/customizations/cloudtrail/validation.py/DigestTraverser._load_and_validate_digest