diff --git a/DEVELOPERS.md b/DEVELOPERS.md
index 6ff577f..e56f691 100644
--- a/DEVELOPERS.md
+++ b/DEVELOPERS.md
@@ -39,7 +39,6 @@ export TEST_ARCHIVIST="https://app.datatrails.ai"
 export TEST_AUTHTOKEN_FILENAME=credentials/.auth_token
 export TEST_NAMESPACE="unique label"
 export TEST_VERBOSE=-v
-export TEST_PROOF_MECHANISM="-i SIMPLE_HASH"
 ```
 
 If TEST_VERBOSE is "-v" debugging output will appear when running the tests.
diff --git a/README.md b/README.md
index cbe5dad..240791b 100644
--- a/README.md
+++ b/README.md
@@ -34,13 +34,10 @@ export TEST_ARCHIVIST="https://app.datatrails.ai"
 export TEST_AUTHTOKEN_FILENAME=credentials/.auth_token
 export TEST_NAMESPACE="unique label"
 export TEST_VERBOSE=-v
-export TEST_PROOF_MECHANISM="--proof-mechanism=SIMPLE_HASH"
 ```
 
 If TEST_VERBOSE is "-v" debugging output will appear when running the examples. Otherwise leave blank or undefined.
 
-TEST_PROOF_MECHANISM should be "KHIPU" or "SIMPLE_HASH". If unspecified the default is "SIMPLE_HASH"
-
 Windows using Powershell - at the command prompt set values for environment variables:
 
 ```bash
@@ -48,7 +45,6 @@ $Env:TEST_ARCHIVIST="https://app.datatrails.ai"
 $Env:TEST_AUTHTOKEN_FILENAME = '<path of token location>'
 $Env:TEST_NAMESPACE = Get-Date -UFormat %s
 $Env:TEST_VERBOSE = '-v'
-$Env:TEST_PROOF_MECHANISM="--proof-mechanism=SIMPLE_HASH"
 ```
 
 TEST_NAMESPACE is set to the date and time value in Unix format, thus providing a unique id upon execution.
@@ -73,7 +69,7 @@ Events are created every execution of an example - currently no check is done if
 All examples use a common set of arguments:
 
 ```bash
-export AUTH="-u $TEST_ARCHIVIST -t $TEST_AUTHTOKEN_FILENAME $TEST_VERBOSE $TEST_PROOF_MECHANISM"
+export AUTH="-u $TEST_ARCHIVIST -t $TEST_AUTHTOKEN_FILENAME $TEST_VERBOSE"
 export ARGS="$AUTH --namespace $TEST_NAMESPACE"
 ```
 
diff --git a/archivist_samples/sample_scripts/c2pa/c2pa_verify.py b/archivist_samples/sample_scripts/c2pa/c2pa_verify.py
index 02a42ea..67706b1 100644
--- a/archivist_samples/sample_scripts/c2pa/c2pa_verify.py
+++ b/archivist_samples/sample_scripts/c2pa/c2pa_verify.py
@@ -15,7 +15,6 @@
 
 from archivist.logger import set_logger
 from archivist.archivist import Archivist
-from archivist.proof_mechanism import ProofMechanism
 from archivist.utils import get_auth
 
 import time
diff --git a/archivist_samples/testing/archivist_parser.py b/archivist_samples/testing/archivist_parser.py
index 29b4acb..868db48 100644
--- a/archivist_samples/testing/archivist_parser.py
+++ b/archivist_samples/testing/archivist_parser.py
@@ -15,7 +15,6 @@
 
 from archivist.archivist import Archivist
 from archivist.logger import set_logger
-from archivist.proof_mechanism import ProofMechanism
 
 LOGGER = logging.getLogger(__name__)
 
@@ -72,16 +71,6 @@ def common_parser(description):
         default="https://app.datatrails.ai",
         help="url of Archivist service",
     )
-    parser.add_argument(
-        "-p",
-        "--proof-mechanism",
-        type=ProofMechanism,
-        action=EnumAction,
-        dest="proof_mechanism",
-        default=ProofMechanism.SIMPLE_HASH,
-        help="mechanism for proving the evidence for events on the Asset",
-    )
-
     parser.add_argument(
         "-t",
         "--auth-token",
@@ -104,17 +93,12 @@ def endpoint(args):
 
     arch = None
     LOGGER.info("Initialising connection to DataTrails...")
-    fixtures = {
-        "assets": {
-            "proof_mechanism": args.proof_mechanism.name,
-        },
-    }
 
     if args.auth_token_file:
         with open(args.auth_token_file, mode="r", encoding="utf-8") as tokenfile:
             authtoken = tokenfile.read().strip()
 
-        arch = Archivist(args.url, authtoken, fixtures=fixtures)
+        arch = Archivist(args.url, authtoken)
 
     if arch is None:
         LOGGER.error("Critical error.  Aborting.")
diff --git a/requirements.txt b/requirements.txt
index 9cbd1c7..027435f 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -7,4 +7,4 @@ pyyaml~=6.0.1
 # the following lines. Also do similar in the Dockerfile.
 # That way one can test an unreleased version of github datatrails-samples.
 # NB dont forget to uncomment before merging !!
-datatrails-archivist==0.30.0
+datatrails-archivist==0.31.0
diff --git a/scripts/api.sh b/scripts/api.sh
index 168c76e..34fa9f1 100755
--- a/scripts/api.sh
+++ b/scripts/api.sh
@@ -17,7 +17,6 @@ docker run \
     -e TEST_NAMESPACE \
     -e TEST_SELECTOR \
     -e TEST_VERBOSE \
-    -e TEST_PROOF_MECHANISM \
     -e GITHUB_REF \
     -e TWINE_USERNAME \
     -e TWINE_PASSWORD \
diff --git a/scripts/samples.sh b/scripts/samples.sh
index 5f7873f..285d784 100755
--- a/scripts/samples.sh
+++ b/scripts/samples.sh
@@ -83,7 +83,7 @@ do
 done
 
 export PYTHONWARNINGS="ignore:Unverified HTTPS request"
-ARGS="-u $TEST_ARCHIVIST -t $TEST_AUTHTOKEN_FILENAME $TEST_VERBOSE $TEST_PROOF_MECHANISM"
+ARGS="-u $TEST_ARCHIVIST -t $TEST_AUTHTOKEN_FILENAME $TEST_VERBOSE"
 
 # namespacing ensures that each run  of the tests is independent.
 if [ -n "$TEST_NAMESPACE" ]