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.

TagViewTree.png


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.

TagViewXML.png

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.    


TagViewText.png

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:

 
ElemViewTree.png

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:

HexViewBytes.png

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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