Provided are methods and apparatuses for providing and using content allowing integrity verification for determining whether the content has been altered. In examples, the headband includes first and second loops supporting the headband on a wearer’s head, and an adjustment mechanism for tightening the first and second loops. An insulating core within the annulus encases lengthwise the inner pipe, and comprises a plurality of pre-cured syntactic elements. For example, one or more Eigenvalues of the matrix can be identified, and a determination can be made whether a second smallest Eigenvalue equals zero.