Algorithmic thinking is an important part of digital literacy, enabling learners to navigate the digital world with confidence. As part of a Design Research study with 22 learners in grades 5 and 6 so far, it was investigated to what extent the children learn to think algorithmically when they discover an encryption algorithm without use of a programming language. It was found that some learners can intuitively and independently develop certain algorithmic thinking ideas (such as sequencing and loops) when writing instructions (=developing an algorithm). Hurdles show up in the degree of precision and the degree of generality of the instructions.