Message Views
ASN1VE allows two different views of a loaded message:
Tag View
Tag view is the default view and is shown when no ASN.1
schema is loaded. It is applicable to BER/DER/CER messages only since PER messages have no defined structure without knowledge of the ASN.1 schema.
This display shows the built-in tags, lengths,
and values in the message. A value is only decoded when
it can be interpreted based on a UNIVERSAL tag (for example,
if an item is tagged with the UNIVERSAL INTEGER tag, then
its contents can be decoded as an integer).
The tree hierarchy located on the left hand side of
the application will show the internal structure of the
BER/DER message by showing
all of the tagged value containers.
Each layer can be expanded/contracted by double-clicking
on the tagged element or by clicking on the +/- box next
to the element.
The BER/DER binary message
data will be displayed as a Hex dump, XML message or Text
data in the upper right hand side of the application.
Hex
Tab
This will display the detail of the selected node related
binary data with color-coding as follows:
The data highlighted in the Hex view corresponds to
the tagged element selected in the tree window. The offset of the data in the message can be determined
by the "Offset" or "Address" column.
Clicking on the Address/Offset button
will cause the display to toggle between Hex (Address)
and decimal (Offset) display modes. Each byte's offset
value will be displayed in a tooltip.
XML
Tab
The XML Tab will display the decoded message as an XML message.
The XML message will be created with the following two
parameters:
- XML element name as the decoded tag name.
- XML element value as the decoded value for tag
as follows:
- If the tag is a known ASN.1 type (i.e. a UNIVERSAL
tag), then the value is decoded and displayed in
its decoded form.
- If the tag is not a known ASN.1 type, then
the value is displayed as a hex representation
of the data in encoded form.
Text
Tab:
Text tab will display the decoded message in a brace text format. The element name will be the tag name. The value
for the element would be the hex data or actual decoded
value of the tag as above.
The detail view window provides additional information
on the item selected tag in the tree window. The following
information is shown:
Offset |
Position
of the data in the binary message. |
Type |
The
name of the ASN.1 built-in type is displayed if
the type can be determined from the tag value
(i.e. if it is an ASN.1 universal tag). |
Tag |
Information
on the class, form and identifier of the ASN.1
tag value. |
Length |
Length
of the data element in octets. |
Value |
If
the value type can be determined (i.e. if it is
an ASN.1 built-in type with an explicit universal
tag), the decoded contents value is displayed. |
Element View
Element view associates each of the tagged elements
in the message with it's corresponding name from the ASN.1
schema. This view is displayed after a schema is loaded
that contains a PDU type that matches the message. A name
is associated with each item in the message. Also, type
information in the schema makes it possible to decode
the contents of all of the data fields. The decoded contents
of each field are displayed in the data window in the
lower right section of the display.
The element view will be blank if an ASN.1 schema is
not assigned or a PDU type is not selected. By switching
to this view, ASN1VE will decode the message using the
assigned ASN.1 schema. If the message does not match a
PDU type within the schema or if decoding fails, an error
message will be displayed.
The tree view window will show the internal structure of
the BER/DER message with the associated ASN.1 data type
as follows:
Each layer can be expanded/contracted by double-clicking
on the element name or by clicking on the +/- box next
to the element. The binary message data will be displayed as a
Hex dump, XML message or Text data in the binary view window of the application as the following:
Hex
Tab
This will display the detail of the selected node related
binary data with color-coding as follows:
The data highlighted in the Hex tabbed window corresponds
to the element name selected in the tree view.
The element view will display the binary data related with
the element instead of displaying the details of tag, length
and value.
The offset of the data in the message can be determined
by the "Offset" or "Address" column.
Clicking on the "Address"/"Offset"
button will cause the display to toggle between Hex (Address)
and decimal (Offset) display modes. Each byte's offset
value will be displayed in tool tip.
If a PER message is loaded, the display may appear slightly different with green boxes possibly shown on the first and last byte of the selection:
This indicate that only parts of these bytes (leading or trailing bits) are used in the encoding. For full details as to which ones, click the Bit tab.
XML
Tab
The XML tab will display the decoded message as an XML message.
ASN.1 elements will be created as XML elements and values
of the elements will be created using the names from the
schema as XML tags. Values will be displayed in decoded
form inside the XML tags.
Text
Tab
The Text tab will display the decoded message as a brace-text value formatted
message. The ASN.1 element will be written as an element
name and the value of this ASN.1 element will be written
after the '=' sign. The bottom right window will provide
detailed information on the selected element in the left
tree window. The following information is shown:
Offset |
Position of the data in the
binary message. |
Type Name |
The name of the element type
defined in the assigned ASN.1 file. |
ASN.1 Type Name |
The name of the ASN.1 built-in
type for the element type defined in assigned
ASN.1 file. |
Tag |
Information on the class, form
and identifier of the ASN.1 tag value. |
Value |
The decoded contents value.
The value is decoded using the element type found
in the assigned ASN.1 file. |
Bit
Tab
The Bit tab will display the actual bit fields that make up an encoded message. It is only applicable to PER since PER messages can begin and end on bit boundaries, therefore this tab is not displayed when a BER/DER/CER message is loaded. An example of what is displayed is as follows:
This corresponds to the hex view of the PER message shown above. As can be seen, the beginning and end bytes are partial.
Positioning the cursor over any byte in the bit field display will cause the hexadecimal code of the byte to be shown as a tool tip.
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