A method of storing digital data into peptides comprising: encoding the digital data into a digital code; translating the digital code into the peptide sequences, wherein an individual peptide sequence comprises a sequence of amino acids corresponding to a part of the digital code such that the part of the digital code is carried in the individual peptide sequence, an individual amino acid in the sequence of amino acids representing a pattern of bits or symbols; and synthesizing the translated peptide sequences into the peptides; characterised in that : the encoding of the digital data into the digital code comprises adding one or more order-checking bits into the part of the digital code, the one or more order-checking bits being used for protecting the order of selected bits or symbols in the part of the digital code and being generated based on one or more orders of the selected bits or symbols, the selected bits or symbols consisting of first and second sequences of patterns of bits or symbols, the first sequence of patterns of bits or symbols being located at one end of the individual peptide sequence while the second sequence of patterns of bits or symbols is located at another end thereof; and each peptide is generated from one translated peptide sequence such that a respective peptide synthesized from the individual peptide sequence carries the one or more order-checking bits, the one or more order-checking bits in the respective peptide assisting selection of a single candidate sequence to be the individual peptide sequence among plural candidate sequences each having a length of the individual peptide sequence and each obtained from a peptide sequencing method used in tandem mass spectrometry analysis when the respective peptide is sequenced during retrieving the digital data from the peptides. encoding the digital data into a digital code; translating the digital code into the peptide sequences, wherein an individual peptide sequence comprises a sequence of amino acids corresponding to a part of the digital code such that the part of the digital code is carried in the individual peptide sequence, an individual amino acid in the sequence of amino acids representing a pattern of bits or symbols; and synthesizing the translated peptide sequences into the peptides; the encoding of the digital data into the digital code comprises adding one or more order-checking bits into the part of the digital code, the one or more order-checking bits being used for protecting the order of selected bits or symbols in the part of the digital code and being generated based on one or more orders of the selected bits or symbols, the selected bits or symbols consisting of first and second sequences of patterns of bits or symbols, the first sequence of patterns of bits or symbols being located at one end of the individual peptide sequence while the second sequence of patterns of bits or symbols is located at another end thereof; and each peptide is generated from one translated peptide sequence such that a respective peptide synthesized from the individual peptide sequence carries the one or more order-checking bits, the one or more order-checking bits in the respective peptide assisting selection of a single candidate sequence to be the individual peptide sequence among plural candidate sequences each having a length of the individual peptide sequence and each obtained from a peptide sequencing method used in tandem mass spectrometry analysis when the respective peptide is sequenced during retrieving the digital data from the peptides. <EOS>