Learn English – “Masters degree” — capital M or not

You would not capitalize "standard" because it is not a proper noun.

Think about it this way, if you were to be taking about a city named "San Franciso" rather than a standard named ISO 1923801: The Proper Use of Capital Letters you would not capitalize later instances of the word "city."

I visited the city of San Franciso. I found the city to be delightful.

If you wanted to be very clear in your text, you can give the work an alias, using parentheses.

For example:

I spent a lot of time on the popular standard on capitalization ISO 1923801: The Proper Use of Capital Letters ("the Standard"). Further perusals of the Standard continued to be useful.

You will find this type of device more often in legal documents.

To quote the relevant sections of the Chicago Manual of Style (CMoS):

8.28 Names of degrees, fellowships, and the like are lowercased when referred to generically.

8.84 Academic subjects are not capitalized unless they form part of a department name or an official course name or are themselves proper nouns (e.g., English, Latin).

So if you were to follow CMoS, you would write:

I hope to one day go on to complete a master's degree in computer science, with a focus in applied cryptography.

CMoS notes in 8.85 that "official names of courses of study are capitalized." So if you wanted to highlight that you "took Bruce Schneier's Applied Cryptography 420 course," capitalizing "applied cryptography" would be appropriate in that case.