A cryptologic system comprising: memory ; a blockchain stored within the memory , the blockchain comprising: a first block (B2, 106, 202) comprising original data; and a second block comprising: a first integrity output (IC(B0), ..., IC(Bn-1)) computed using the original data as an input; and a second integrity output (IC(B0), ..., IC(Bn-1) computed using the original data as an input; characterized in that the system comprises circuitry configured to: determine, using a first key secret , collision data including altered data, the collision data being coding-consistent with the first integrity output (IC(B0), ..., IC(Bn-1)) and coding-inconsistent with the second integrity output (IC(B0), ..., IC(Bn-1)); perform a tamper-evident rewrite of the blockchain by replacing the original data with the collision data; and generate a rewrite artifact in the blockchain by rewriting the first block (B2, 106, 202) with the altered data being different than the original data, the altered data coding-consistent with the first integrity output (IC(B0), ..., IC(Bn-1)) but coding-inconsistent with the second integrity output (IC(B0), ..., IC(Bn-1)). memory ; a blockchain stored within the memory , the blockchain comprising: a first block (B2, 106, 202) comprising original data; and a second block comprising: a first integrity output (IC(B0), ..., IC(Bn-1)) computed using the original data as an input; and a second integrity output (IC(B0), ..., IC(Bn-1) computed using the original data as an input; characterized in that the system comprises a first block (B2, 106, 202) comprising original data; and a second block comprising: a first integrity output (IC(B0), ..., IC(Bn-1)) computed using the original data as an input; and a second integrity output (IC(B0), ..., IC(Bn-1) computed using the original data as an input; a first integrity output (IC(B0), ..., IC(Bn-1)) computed using the original data as an input; and a second integrity output (IC(B0), ..., IC(Bn-1) computed using the original data as an input; characterized in that the system comprises circuitry configured to: determine, using a first key secret , collision data including altered data, the collision data being coding-consistent with the first integrity output (IC(B0), ..., IC(Bn-1)) and coding-inconsistent with the second integrity output (IC(B0), ..., IC(Bn-1)); perform a tamper-evident rewrite of the blockchain by replacing the original data with the collision data; and generate a rewrite artifact in the blockchain by rewriting the first block (B2, 106, 202) with the altered data being different than the original data, the altered data coding-consistent with the first integrity output (IC(B0), ..., IC(Bn-1)) but coding-inconsistent with the second integrity output (IC(B0), ..., IC(Bn-1)). determine, using a first key secret , collision data including altered data, the collision data being coding-consistent with the first integrity output (IC(B0), ..., IC(Bn-1)) and coding-inconsistent with the second integrity output (IC(B0), ..., IC(Bn-1)); perform a tamper-evident rewrite of the blockchain by replacing the original data with the collision data; and generate a rewrite artifact in the blockchain by rewriting the first block (B2, 106, 202) with the altered data being different than the original data, the altered data coding-consistent with the first integrity output (IC(B0), ..., IC(Bn-1)) but coding-inconsistent with the second integrity output (IC(B0), ..., IC(Bn-1)). <EOS>