Change:
The following example illustrates a registrar voucher-request. The 'prior-signed-voucher-request' leaf is populated with the pledge's voucher-request (such as the prior example).  The <del> pledge's voucher-request, if a signed artifact with a CMS format signature is a binary object.  In the JSON encoding used here it must be base64 encoded.  The nonce, created-on and assertion is carried forward.  The serial-number is extracted from the pledge's Client Certificate from the TLS connection.  See </del> <ins> pledge's voucher-request is a binary object.  In the JSON encoding used here it must be base64 encoded.  The nonce, created-on and assertion is carried forward.  The serial-number is extracted from the pledge's Client Certificate from the TLS connection.  See </ins> RequestVoucherFromMASA. The following example illustrates a registrar voucher-request.

Discussion:
This should be a complete set of diffs for removing unsigned pledge voucher-requests from the text.
For issue
The text "This artifact may be optionally signed" is buried in the yang module (ietf-voucher-URL) and needs to be removed.
When a pledge decides to use an unsigned voucher request, the Registrar will place it into prior-signed-voucher request on the BRSKI-MASA arc. It will be JSON embedded in. When a pledge decides to use a signed voucher request, the Registrar will place the base64 encode of the pledge_request in as a string. The MASA can tell the difference between the two because the signed thing (whether CBOR, COSE, CMS signed CBOR, or CMS signed JSON) will always be base64 encoded. We need to explain this somewhere.
section 5.5 indicates that: prior-signed-voucher-request: If a signed pledge voucher-request was received then it SHOULD be included in the registrar voucher- request. (NOTE: what is included is the complete pledge voucher- request, inclusive of the 'assertion', 'proximity-registrar-cert', etc wrapped by the pledge's original signature). If a signed voucher-request was not recieved from the pledge then this leaf is omitted from the registrar voucher request. This indicates that the MASA never needs to "tell the difference" only the registrar. (The pledge to registrar signaling is via request media type as detailed in s5.2). I did notice this when reading: s3.3. these references to voucher in the leaf description should be to voucher request? "If it is necessary to change a voucher, or re-sign and forward a voucher that was previously provided along a protocol path, then the previously signed voucher SHOULD be included in this field." etc. subsequent paragraphs.
URL tries to fix the lack of specification for unsigned voucher requests.
Max to produce a draft branch that removes unsigned voucher request so we can examine the ramifications of this.
v20 of BRSKI removed unsigned voucher requests. What were the reasons for removing? I don't see a mention of this in the anima WG email. If removed as a final decision, then this issue can be closed also.
Hi, yes, we could close this now. I did post several times to the list in Feb and March, and it was raised during the WG meeting itself, asking for feedback.

Ok, I now see the email list discussion also in December 2018 and based on this the unsigned voucher was removed.